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Subsections

Phytopathology

Diseases of plants can cause great crop damages which may lead to hunger disasters of great part of populations. Basic knowledge of the diseases of plants and their cause are therefore important for everyone handling foods.
Despite all efforts to reduce crop damage due to plant diseases using agrochemicals in the past 30 years the loss of approximately 10% remained unchanged. As the crops have increased the total loss is increasing rapidly. This makes a better understanding of phytopathology necessary[1].
Phytopathology wants to bring a better understanding on the cause, the circumstances and the progress of diseases of plants as well the interaction of hos-pathogenic agent.
Phytopathogenic agents are not pathogenic to mankind as moulds and bacteria known as phytopathogenic cannot grow at 37° or are eliminated by immunology of mankind. Phytopathogenic virus need plant louse or gnome zicada as vectors as they cannot penetrate by itself. Human skin is not attractive for these insects. The infection of these virus is therefore not possible.
However allergies to the spores of moulds such as Aspergillus and Penicillium sp. and mycotoxins are of great importance.

Image Planthysto


The evolution of diseases in plants

Diseases in plants develop in different phases:

Phases of a disease caused by mould

Infection period

The infection period is the time between the first attack of the plant by the pathogen agent and the moment in which he has established itself in the tissue of the host.

Incubation period

The incubation period includes the infection period and ends with first macroscopic symptoms.

Fructification period

Is the time between Infection and the first reproduction of the agent in the host.

Some moulds have short periods and the whole life cycle takes only days such as:
Polymyxa
Phytium
Olpidium

Some moulds need over half a year to complete their life cycle such as:

Phases of a disease caused by other agents

viral agents,bacteria, mycoplasma-like organism (MLO) and Rickettsia-like Organism (RLO) present a great reproduction with high number of organism before the fist symptoms appear.


Vectors of phytopathogenic agents

Bacteria such as Xylella fastidiosa, spiroplasma, mycoplasma-like Organism (MLO) and Ricketsia-like organism (RLO) need the help of other living cells or small animals like gnome zicade as vectors to invade another host


The cause of plant damage

Condition for a disease of plants

Susceptible to the disease

The host must be susceptible to the disease. Some plants are resistant to different agents.

Organ specific activity

There must be an organ specific activity of the agent. Some agents can infest only specific organs like flowers or roots to which they are specialized. They cannot invade other parts of the plants.
Examples of organ specific activity are: Polymyxa betae for instance can only attac roots of beets.

Phase specific activity

Some agents have a specific activity to flowers. They have wait till the blossoms open to attack the host, other have a phase specific activity to leaves. they have to wait for the phase of leaves of a plant which is growing from a seed.

Survival of the agent

Some agents have developed survival strategies to overcome the time between one host to another. Virus cannot survive for long time outside a host cell. They need therefore a vector cell to get through the time between where there are no host cells available.The spores of the mould Polymxa can serve as vector for the beet necrotic yellow vein furovirus for a period of many years. Other agents have a saprophytic phase surviving in dead tissue of the host of the culture period to another season to start a new outbreak of disease.

Saprophytic decomposition

Some saprophytes may decompose cell walls of dead material this activity also can include living phytopatological agents. Mucor and Rhizopus moulds can decompose cellulose of the cell of dead materials disclosing pathogen virus which had invaded these cells. The virus is now unprotected and will soon be damaged.
Agrochemicals can interfere in the cycle of nature destroying normal saprophytes which are enemies of harmful pathogenic agents.

Competition of nutrients

Saprophytic bacteria can multiply within an half hour. Pathogen mould need days to multiply being so in disadvantage on regard of nutritional resources.

Production of antibiotics

Some moulds like Penicillium sp and Streptomyces sp =produce antibiotics which act as natural enemies of some phytopathogen agents. Interfering in the natural environment may destroy useful saprophytes boosting pathogens.

Virus with mycopathogenic activity

Some virus act toxic on pathogenic moulds. The protection of the natural environment is therefore important. Modern agricultural techniques should protect the complex interaction of th different biological systems.

Hyperparasites

A parasite with phytopathologic activities may be invaded on its turn, by other parasites ,like nematodes, bacteria and bacteriophages.

Parasitic plants can be half parasites having well developed leaves. They depend only from water and minerals from the xylem of the host (Loranthaceae, Viscaceae, Scrophulariaceae.
Full parasites have underdeveloped or no leaves at all. They invade the xilem and the phloem of their host and get there nourishing substances
Mistletoe    
Loranthus europaeus South Europe Oak tree
Arceuthobium sp North America, Himalaya conifer
Viscum album ssp album Europe Apple, poplar
Viscum album ssp.abietes Europe Fir tree
Convolvulaceae    
Cuscuta europea Europe Hop, shrubs, sugar beets
Cuscuta campestris worldwide Legume, sugar beet
Cuscuta reflexa Southeast Asia Citrus, Coffee, Litchi
Scrophulariaceae    
Striga asiatica worldwide,except Europe Maize,sorghum, millet, sugar cane
Orobanchaceae    
Orobanche cernua Mediterranean region Sunflower
  East Europe,Africa  
Orobanche crenata Mediterranean region Beans, lentil, chick pea
Orobanche ramosa Mediterranean region Tobaco, tomato, aubergine
  Africa, Zentral and North America  

Microbes as agents of plant diseases

Virus: have only one type of nucleic acid, most of the time RNA, seldom DNA. Energy system ATP does not exist. Virus depend on ribosomes of host cells.
Mycoplasma-Like Organism (MLO)
Rickettsia-Like Organism (RLO)
Bacteria
Moulds
MLO, RLO, bacteria and moulds have usually both types of nucleic acids (RNA and DNA). Energy system ATP exists and they can multiply without aid of a host cell.


Phytopathogenic virus

Cauliflower mosaic (Caulimo): It is build of DNA.
Bacilus-shaped DNA (Badna)
Gemini virus
Phytoreo virus
Rhabdo virus
Tomato spotted wilt (Tospo)
Tenui virus
Cowpea mosaic virus (Como)
Faba virus
Nematode-transmitted polyeder (Nepo)
Potato virus Y (Poty)
Rye grass mosaic (Rymo)
Barley yellow mosaic (Bymo)
Southern bean mosaic (Sobemo)
Luteo virus
Tomato bushy stunt (Tombus)
Carnation mottle (Carmo)
Tobacco necrosis (Necro)
Diantho virus
Tobacco mosaic (Tobamo)
Tobaco rattle (Tobra)
Hordei virus
Fungus-transmitted, rod shaped virus (Furo)
Clostero virus
Turnip yellow mosaic (Tymo)
Alfafa mosaic (Alfamo)
Isometric labile ringspot (Ilar)
Brome mosaic (Bromo)
Cucumber mosaic (Cucumo)
Carnation latent (Carla)
Potato virus X (Potex)


The mould Pythium irregulare is a plant pathogen [2]

Pythium irregulare root rot and blackleg of geranium is a mefenoxam insensitivity re-emerging disease. The fungus is also commonly isolated from poinsettia, chrysanthemum, snapdragon, impatiens, and lavender. It is also known as downy mildew. Blight, damping off, root and other rots.

Virus of economic importance

Cacao swollen shoot badnavirus: It is a DNA-virus.
Tomato leaf roll geminivirus: DNA-virus.
Cassava mosaic geminivirus: DNA-virus
Rice dwarf phytoreovirus: RNA-virus
Tomato spotted wilt tospovirus
Rice grassy stunt tenuivirus
Barley yellow dwarf luteovirus
Potato leaf roll luteovirus
Beet yellows closterovirus
Citrus tristeza closterovirus
Potato virus Y potyvirus
Barley yellow mosaic bymovirus
Tobacco mosaic tobamovirus
Grapevine fanleaf nepovirus
Beet necrotic yellow vein furovirus
Cucumber mosaic cucumovirus
Prunus necrotic ringspot ilarvirus
Alfafa mosaic alfamovirus
Tobacco rattle tobravirus

Pathogen germ Host Disease
     
Gram-negative    
Agrobacterium tumefaciens   tumor
Agrobacterium vitis vine  
Burkholderia solanacearum    
Burkholderia caryophylli clove  
Erwinia amylovora pear and apple  
Erwinia carotovora potatos  
Pseudomonas savastanoi bush bean  
Pseudomonas syringae    
Xanthomonas axonopodis    
Xanthomonas campestris cabbage  
Xantomonas hortorumpelargonium    
Xanthomonas oryzae rice  
Xanthomonas transluceus wheat  
     
Gram-positive    
Clavibacter michiganensis tomato  
Rhodococcus fascians pea  
Streptomyces scabies potato  

Phytopathogenic moulds

Aspiognomonia veneta It causes antracnosis on plane-tree.
Cryphonectria parasitica causes disease of chestnut-tree.
Diaporthe perniciosa Causes necrosis of the bark from apple-tree
Leucostoma cincta Causes a disease of the bark of peach-trees.
Cochliobolus sativus Disease of cereals.
Cochliobolus victoriae Victoria disease of oats.
Didymella aplanata Disease of raspberry.
Leptosphaeria maculans Disease of the roots of rape.
Mycosphaerella arachidicola Spots on leaves of the peanut-plant.
Mycosphaerella graminicola Spots on leaves of wheat.
Mycosphaerella musicola Disease of banana.
Phaesphaeria nodorum Disease of wheat.
Pyrenophora chaetomioides Disease of oats.
Pyrenophora graminea Disease of barley.
Pyrenophora teresDisease of barley.
Venturia inequalis Scab of apple.
Blumeria graminis Disease of cereals: It cannot synthesize purines which are part of nucleic acid. Purines must therefor be taken from the host. It is therefore an obligatory parasite
Leveillula taurica Disease of tomatos.
Podosphaera leucotricha Disease of appel.
Sphaerotheca fuliginia Disease of cucumber.
Uncinula necator Disease of grape plant.
Aspergillus flavusDisease of peanuts.
Penicillium expansum Rot of apple.
Claviceps purpurea Ergotism of wheat. Claviceps purpurea forms ascospores can infect only blossoms. The best conditions of weather for the production of blossoms of the wheat most of the time occurs at a different time of the releae
Builts black sclerots which are formed from mycelium Cibberella fujicuroi Disease of rice.
Cibberella zeaeDisease of maize.
Nectria galligena canker of apple-tree.
Diplocarpon rosae Disease of roses.
Drepanopeziza ribis Disease of redcurrant.
Mollisia acuformis Disease of cereals.
Pezicula malicortis disease of apple.
Pseudopezicola tracheiphila Disease of wine.
Pseudopeziza medicaginis Disease of Spanish trefoil.
Magnaporthe grisea Rice blast.
Taphrina deformans Disease of peach.
Taphrina pruni Disease of prun.
Alternaria solani Stains of the leaves of tomato-plant.
Septoria apiicola Stains of the leaves of celeriae.
Alternaria sp. Black rott of citrus fruit.
Aspergillus sp. Black rott of peach and nectarine.
Aspergillus flavus produce aflatoxin B1. 100mcg in the feed of mice over a long period of time induces liver cancer in rats. Aspergillus flavus contamination of food is very high in Africa. The continent has the highest number of liver cancer events of the world because of the high aflatoxin contamination of vegetable foods. Botryodiplodia sp. Rottenness of the banana-plant.
Botrytis sp. Rottenness of fruits.
Cercospora musaeIs the cause of the Sigatoka disease of banana plantations. To fight the Sigatoka fungus a watery solution of chalk and copper sulphate was sprayed on the plants, later on mineral oil was sprayed by helicopters and crop airplanes.
Environment protection organizations have started a campaign to reduce toxic chemicals in banana plantations. The careless use of chemicals used against moulds and worms as well as weed killers being sprayed by crop planes over banana plantations produce sterility, skin diseases, asthma, damage kidneys and liver of the population living in this area.[3]
Cladosporium sp. Rottenness of fruits.
Colletotrichum sp. Rottenness of citrus fruits, avocados and papayas.
Diaporthe sp. rottenness of citrus fruits.
Diplodia sp. Rottenness of the stem of citrus fruits, avocados, and papayas. Wet rottenness of peach.
Fusarium sp. Brown rottenness of citrus fruits, pineapple and wet rottenness of figs.
Fusarium oxysporum var.cubense This fungus is known as agent of the Panama disease of banana plants. It invades the roots of the plant and destroys a banana farm. In 1925 and 1935 the Fusarium fungus was eliminated by flooding the plantations one by one with a level of one and a half of water. After six months the water was drained and the plantation could be used again for five to six years. This method could be used only in valleys or plains.
Very sensible to Fusarium are the banana sorts Gros Michel. In Brazil, in some parts of Africa and Australia the Cavendish sort is being cultivated, also Lactan and Robusta are sorts which are resistant to the fungus Fusarium.
Geotrichum sp. Acid rottenness of citrus fruits and peaches.
Gibberella fujikuroi is the agent of the Bakanae disease of rice. The fungus Gibberella produces gibberilin acid which is a growth promoter. The growth which is induced by gibbeilin thin and the plant can scarcely carry its own weight. Gibberella also produces a substance which is toxic to the roots of rice. The rice plants die on account of these substances. Gloeosporium sp. Rottenness of pome fruits.
Leptosphaeria maculans Is worldwide the most important pathogen fungus which attacks rape. There are pathogen and not pathogen types.
Monilia sp. Brown rottenness of fruits.
Monilia attacks cherry-trees, killing leaves and branches.
Nigrospora sp. Rottenness of banana pulp.
Penicillium sp. Blue and green rottenness of fruits.
Phomopsis sp. Rottenness of the stem of citrus fruits and avocados.
Phytophthora sp. Rottenness of citrus fruits, apple and strawberry.
Piricularia oryzae causes the Brusone disease blue dots which later change to brown color are the first symptoms. When the invasion takes place at an early stage of the growth of the plant no rice kernels are built. If it takes place later the stalk is bend under the weight of the grain in such a manner that the grain comes together with water or mud and gets lost.
To help against the Brusone disease solutions of mercury compounds and copper compounds were used despite their toxic effects.

The rice stripe virus

Rice stripe virus (RSV) is a member of the Tenuivirus genus. It causes chlorotic stripes, chlorosis, moderate stunting and loss of vigour. Severe infections cause the leaves of the plant to develop brown to grey necrotic streaks. If infection is massive the plant dies. The virus occurs in rice, maize, wheat, oat, foxtail millet and wild grasses of the family Gramineae. It does not infect members of other families.

The virus is transmitted by Laodelphax striatellus and three other planthopper species. It occurs in rice-growing areas of Asia and Russia, and causes significant reduction in rice yield.
Kim et al 2012 identified 21 potential rice stripe virus resistance factors and explained their association with the host resistance factors within a network model. [4]

Gutiérrez et al 2010 studied the genetics of the African rice Oryza glaberrima MG12 (acc. IRGC103544), compared to Oryza sativa ssp. tropical japonica (cv. Caiapó). The authors found a strong segregation distortion on chromosomes 3 and 6, which suggests the presence of interspecific sterility genes. This may help to overcome hybrid sterility barriers between species of rice. Fourteen loci for plant height, tiller number per plant, panicle length, sterility percentage, 1000-grain weight and grain yield were located by the authors at chromosomes 1, 3, 4, 6 and 9. A locus controlling resistance to the Rice stripe necrosis virus was located between SSR markers RM202-RM26406 (44.5-44.8 cM) on chromosome 11. [5]

In a study of Li et al 2012, it was demonstrated that NS3 gene produce the highest expression in both, rice plants and the virus vector, the small brown planthopper, and disease-specific protein (SP) gene was the only gene with highest expression in rice, but was not present in planthopper. [6]

Zhou et al 2012 introduced a RNAi construct containing coat protein gene (CP) and disease specific protein gene (SP) sequences from rice stripe virus into varieties of rice in varieties of rice. The transgenic plants were strongly resistant to viral infection, and viral replication of SP and CP was significantly inhibited. The authors suggest that the introduction of such a RNAi may reduce the vulnerability of rice varieties to the rice stripe virus. [7] Rhizopus sp. Wet rottenness of fruits.
Sclerotinia. White rottenness of strawberry.
Sclerotinia sclerotiorum Is a fungus which causes great damage on rape. This fungus is in vitro highly sensible to alkenile-glucosinolates. Sclerotinia sclerotiorum produces during the invasion of a plant high amount of oxalic acid getting the pH down to 2,0 - 4,0. At the place of the invasion nitriles instead of alkenyles are formed.
Trichoderma sp.Brown-green rottenness of citrus fruits.
Venturia sp. rottenness of fruits.


Black Pod and canker of cocoa trees [8]

The cocoa plant is particularly susceptible to disease from the fungus Black Pod Phytophthora palmivora, affecting the pods and stems, cocoa beans become spoiled. The disease spreads in 2008 in plantations of the Ivory Coast which is the world main producer of cocoa. Other pathogenic moulds affecting cocoa plants are Phytophthora megakarya and a not yet firmly determined species, Phytophtora capsici.

These fungus may cause diseases in other hosts like cashew nut, coconut, rubber, papaya, betelnut palm, black pepper, pineapple, oil palm, breadfruit and others.

Chemical control of black pod by spraying with copper based fungicide is widely used, depending on the timing of rainfall, age of the trees, shade and other local conditions.

Trunk injection of solution of phosphoric acid is described as a chemical treatment to control stem canker. [9]

The pathogen infects the leaves, shoots, flower cushion, roots and pods which turn black.

When the disease spreads to the bark of the stem or branch it cause a canker. The spores of the fungus is spread by rain, wind, flying beetles, all kind of insects, bats and rodents.

Processing and chocolate manufacturing are in the hands of Barry Callebaut, Cargill and Archer Daniels Midland, and Nestlé.

Sudden Oak Death

Sudden Oak Death is the disease caused by the fungus-like pathogen Phytophthora ramorum that is causing extensive damage and mortality to oak and other species of tree in California and Oregon and Europe. Symptoms include bleeding cankers on the trunk and dieback of the foliage. In Europe it was found affecting rhododendron, viburnum and camellia. Its spread was recently observed on Japanese larches in Wales, Northern Ireland and the Republic of Ireland. See Photos [10] [11]

Ramorum dieback [12]

At rhododendrons Phytophthora ramorum causes a non-fatal foliage disease known as ramorum dieback. Such plants can act as a source of the inoculum for the disease, with the pathogen producing spores that can be transmitted by wind and rainwater. Very few control mechanisms exist for the disease, and they rely upon early detection and proper disposal of infected plant material.

General sanitation in infested areas [12]

One of the most important aspects of Phytophtora ramorum control involves interrupting the human-mediated movement of the pathogen by ensuring that infested materials do not move from location to location. While enforceable quarantines perform part of this function, basic cleanliness when working or recreating in infested areas is also important. In most cases, cleanliness practices involve ridding potentially infested surfaces - such as shoes, vehicles, and pets - of foliage and mud before leaving the infested area.

Early detection of Phytophtora ramorum [13]

Early detection of Phytophtora ramorum is essential for its control. Preventative treatments depend on knowledge of the pathogen's movement through the landscape to know when it is nearing prized trees. Detection methods are:

Culturing The traditional method of culturing is on a growth medium that is selective against fungi (and, in some cases, against other oomycetes such as Pythium species). Successful isolation of the pathogen often depends on the type of host tissue and the time of year that detection is attempted.

The ELISA (enzyme-linked immunosorbent assay) test Elisa test can detect the presence of proteins that are produced by all Phytophthora species. Elisa does not distinguish between Phytophtora ramorum and other Phytophtora spp.

Amplifying DNA sequences Amplifying DNA sequences in the internal transcribed spacer region of the Phytophtora ramorum genome (ITS Polymerase Chain Reaction, or ITS PCR); real-time PCR, in which DNA abundance is measured in real time during the PCR reaction, using dyes or probes such as SBYR-Green or TaqMan; multiplex PCR, which amplifies more than one region of DNA at the same time; and Single Strand Conformation Polymorphism (SSCP), which uses the ITS DNA sequence amplified by the PCR reaction to differentiate Phytophthora species according to their differential movement through a gel.

To improve distinction between the species of Phytophtora researchers use the amplified fragment length polymorphism, which through comparing differences between various fragments in the sequence has enabled researchers to differentiate correctly between EU and U.S. Isolates, and the examination of microsatellites, which are areas on the sequence featuring repeating base pairs.

Early detection of Phytophtora ramorum on a landscape scale It is based on the observation of symptoms on individual plants, or monitiring watercourses.

Aerial surveying It has proven useful for detection of Phytophtora ramorum infestations across large landscapes, however, it is not an early method, because it spots dead tanoak crowns, when damage already occurred.

Detection of Phytophtora ramorum in watercourses This early detection method is important , because watercourses are an important transport way of oospores of Phytophtora ramorum, employing pear or rhododendron baits suspended in the watercourse using ropes, buckets, mesh bags, or other similar devices.

Engaging local landowners Landowners are asked to send samples to a central laboratory, improving maping of Phytophtora ramorum distribution in the areas.

Garlic white rot on organic muck fields [14]

Hovius and McDonald determine the efficacy of synthetic diallyl disulfide (DADS) to fight white rot of onions grown on organic muck soil. The authors concluded that DADS and to a lesser extent di-N-propyl disulfide (DPDS) effectively reduced the incidence of Allium white rot on onions grown on muck soils. Soil treatment with DADS.

According to the authors Sclerotium cepivorum Berk causes the disease white rot on several Allium family, such as Allium cepa L., Onions, leeks, garlic, chives, shallots and salad onions The disease is significant on organic soils.

Sclerotia germination and host infection are stimulated by alkenyl L-cysteine sulfoxides released by garlic and onions. Garlic root exudates are precursors of the volatile allyl and propyl sulfides that stimulate eruptive germination of the sclerotia.

Germination can be stimulated by products such as natural onion and garlic oil, or synthetic germination stimulants derived from petroleum, such as diallyl disulfide (DADS), a primary decomposition product of allicin.

When the sclerotia germinates, it develops a mycelium which becomes susceptible to hyperparasitism and lysis. In the absence of a host, the fungus dies without reproducing. Two applications of the synthetic germination stimulant DADS, but not DPDS or garlic oil in consecutive years resulted i9n significant reduction of onion infection on organic.

Soils should be treated when the soil temperatures are between 10 and 20° and will remain remain in this range for approximately 3 months with good uniform spread of the stimulant.

Genetic of plant disease-causing bacteria

Virulence gene complement olive knot disease causing Pseudomonas savastanoi [15]

Pseudomonas savastanoi pv. savastanoi NCPPB 3335 is a tumour-inducing pathogen of Olea europaea L. causing olive knot disease. Rodríguez-Palenzuela and colleagues 2010 analysed the genome sequence of Pseudomonas savastanoin revealing similarities with Pseudomonas syringae pv. phaseolicola 1448A and Pseudomonas syringae pv. Tabaci 11528.

The authors report that twelve variable genomic regions of NCPPB 3335 contains twelve variable genomic regions which are not present in Pseudomonas syringae. These genes make the strain capable to survive in a plant host, and 73 predicted coding genes that are NCPPB 3335-specific were found in Pseudomonas savastanoi pathovar indicating specific adatations of P savastanoi.

Prevail of Pseudomonas savastanoi pv. savastanoi type III mutant in olive plants [16]

Pérez-Martínez and colleagues 2010 describe the sequencing of the hrpS-to-hrpZ region of NCPPB 3335, elucidating its phylogenetic position relative to Pseudomonas syringae hrp clusters.

The authors report the construction of a mutant of NCPPB 3335, termed T3, with deletion of the 3' end of the hrpS gene to the 5' end of the hrpZ operon. T3 mutant does not induce tumor formation in woody olive plants, however, it can induce knot formation on young micropropagated olive plants, but without necrosis and formation of internal open cavities, seen with wild-type strain and differed in distribution within the host tissue.

Virulence determining genes in Pseudomonas syringae [17]

Lindeberg and colleagues 2008 describe the virulence-associated genes for three Pseudomonas syringae strains. These genes, described in the DC3,000 genome annotation are associated with the ability to grow on plant surface, to segregate plant- and insect-active toxins, and virulence regulators.

The authors highlight a strong segregation of the HrpL regulon with variable genome regions (VR), whose distribution, together with other sequenced bacterial genomes were discussed by the authors as a virulence sources.

Pseudomonas syringae equipped with an Atypical Type III Secretion System [18]

Christopher and colleagues 2010 stress that Pseudomonas syringae causes a plant disease by translocating immune-suppressing effector proteins into plant cells through a type III secretion system (T3SS).

The authors describe a new Phrp/hrc cluster which differs from the typical Pseudomonas syringae hrp/hrc cluster coding for a T3SS. This new hrp/hrc cluster misses the genes hrpK and hrpS, of the classical P. syringae hrp/hrc cluster. The group 2c strain also revealed distant similarities with the Pseudomonas syringae effector genes avrE1 and hopM1 and the P. aeruginosa effector genes exoU and exoY.

Two virulence domains of AvrPto are conserved in different Pseudomonas syringae [19]

Hanh and colleragues 2010 write that the Pseudomonas syringae pv. tomato type III effector protein AvrPto encode virulence in susceptible tomato plants and also defence responses in resistant tomato and tobacco genotypes. The authors stress that two virulence domains of AvrPto are conserved in diverse pathovars and may be active during infection of diverse plant species.

Pseudomonas syringae pv. tomato DC3000 Type III Effector HopAA1-1 redundant with chlorosis-promoting factor PSPTO4723 to produce bacterial speck lesions in tomato [20]

Cathy and colleagues 2009 report that Pseudomonas syringae pv. tomato DC3000 kill yeast and promote bacterial speck disease in tomato by injection of 28 Avr/Hop effector proteins HopAA1-1, using the type III secretion system.

Deleting hopAA1-1 from DC3000 reduces the formation of necrotic speck lesions in tomato leaves if effector-gene cluster IX or just PSPTO4723 within this region has been deleted. PSPTO4723 does not encode an effector and is associated with chlorosis.

Studying host specificity of Pseudomonas syringae [21]

According to Lindeberg and colleagues 2009 Pseudomonas syringae, using the type III secretion system, injects effector proteins that suppress basal innate immunity of the host cytoplasm. This, however, may be recognized by cognate resistance (R) proteins in a second level of the host defence. Following latest data the nature and evolution of P. syringae host specificity and nonhost resistance may now be further elucidated. [22]

Common toxin fold explains interaction between microbial attack and plant [23]

Ottmann and colleagues 2009 describe the necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) which trigger leaf necrosis and immunity-associated responses in various plants. The authors found that NLP-mediated phytotoxicity and plant defence gene expression share identical fold requirements, indicating that toxins trigger plant immunologic responses. These NLPs proteins present fold similarities to toxins produced by marine organisms like actinoporins. Structure of NLPs from Phytophthora parasitica and Pectobacterium carotovorum, revealed a high extent of this fold conservation. The authors also stress that plant defences activated by these toxins are reminiscent of microbial toxin-induced inflammasome activation in vertebrates suggesting a link between animal and plant innate immunity.

Biologic control of the invasive chilli thirps, Scirtothrips dorsalis

The invasive chilli thrips, Scirtothrips dorsalis Hood poses a significant risk to many food and ornamental crops in the Caribbean, Florida and Texas. It feeds on leaves, turns them brown, kills new growth and attacks up to 150 crops, including peppers, strawberries, tomatoes, peanuts, cotton and a variety of ornamentals.

Arthurs and colleagues tested two species of phytoseiid mites Neoseiulus cucumeris and Amblyseius swirskii as predators of Scirtothrips dorsalis. Biologic control may avoid chilli thirps to become resistant to insecticides. According to the authors, the mites were effective in reduction of the number of thrips, whereas Amblyseius swirskii was the most effective compared with Neoseiulus cucumeris. A good foto documentation may be found at http://www.mrec.ifas.ufl.edu/lso/thripslinks.htm.


Goldspotted oak borer kills oaks in Southern California [24]

According to Coleman and Seybold the Southern California beetle Agrilus coxalis is a wood-boring beetle. It is also known as goldspotted oak borer. Larval feeding kills patches and strips of the phloem and cambium resulting in crown die back followed by mortality.

Oaks (Quercus spp.) are the dominant tree species in Southern California, but 67% of the trees were attacked by the beetle. Their reduction of oaks by the pest will reduce wildlife diversity and increase fire danger. The trees are getting more succeptible to the beetle because of the stress imposed by drought and climate change.

Oak processionary moth may pose risk to European trees says EFSA [25]

According to an opinion of the European Food Safety Authority (EFSA) the oak processionary moth (Thaumetopoea processionea) pose a potential risk to oak trees in southern areas of the UK, and may be considered eligible for addition to the EU list of harmful organisms.

The Panel says that the absence of natural barriers facilitates the spread of the moth by natural dispersal, such as flight, to adjacent areas. The availability of oak and low summer temperatures might hinder the dispersal, but due to changing climate conditions the pest may also spread to southern parts of the most northern European States.

The opinion notes that the oak processionary moth lays eggs on branches of oak trees and its larvae live in groups and form a nest from which they migrate in procession to feed in the canopy of the tree resulting in partial or complete tree defoliation. The caterpillar is also a heath risk for humans and animals because they produce hairs which may cause allergic reactions.

Ambrosia beetle may endanger U.S. Avocado trees [26] [27]

According to Koch and Smith 2009 the avocado production may be seriously hit by the Redbay Ambrosia beetle (Xyleborus glabratus Eichhoff), mowing to the south of the USA.

Lauret wilt

Lauret wilt is a disease of redbay and sassafras (Sassafras albidum) trees caused by the fungus Raffaelae lauricola. The fungus lives in association with the Ambrosia beetle (Xyleborus glabratus) which bores into the sapwood of redbay and sassafras (Sassafras albidum) trees. The female beetle carries spores of the fungus Raffaelea lauricola. The beetles and their larvae feed from the fungus, which germinates in the sapwood and cause tree death, a plant disease called laurel. Avocado trees (Persea americana) and other Lauraceae trees of the coastal Florida, Georgia, and South Carolina are endangered.

The authors stress that Raffaelea lauricola differs from other Raffaelea species in its DNA sequence and spore sizes and grows faster than similar fungi. It also harms shrubs like the pondberry (Lindera melissifolia) [28] and pondspice(Litsea aestivalis, L.) [29].

Some authors suggest the use of fungicides to protect avocado trees other opt to isolate and remove any infected trees as soon as they begin to show signs of wilting. Disruption of human caused, long-distance dispersal, however, are seen by Koch and Smith, as the most effective measure to control the spread of the beetle and fungus.

California Bay Laurel is also a tree which was found succeptible to the fungus Raffaelae lauiricola. Another fungus which can infect the California laurel is oomycete plant pathogen Phytophthora ramorum causing a disease known as Sudden Oak Death. The pathogen will take advantage of wounding, but it is not necessary for infection to occur [30].

Mediterranean fruit fly

The Mediterranean fruit fly Ceratitis capitata attacks fruits, vegetables and nuts. The female Mediterranean fly mates once in her life span depositing the sperm in the female sperm-storing organ, the spermatheca. The female produces 250 - 1,200 eggs which can be fertilized with the stored sperms from the spermatheca.
The fertilized eggs are deposited beneath the outer surface of fruit and vegetables hatching into maggots which then feed on the pulp of the fruit or vegetable spoiling them. Matured maggots drop to the ground, form pupae and eventually emerge as new flies, completing the life cycle.
The fly originated in West Africa from where it spread out to North and South Africa. As the eggs are hidden under the skin of fruits the fly can easily be exported to all parts of the world. The fly is now being found in Europe, Middle East, Australia and South America.


Key program of USA against the Mediterranean fruit fly

In California the Mediterranean fruit fly was seen for the first time in 1975. USA has a key program against the fruit fly distributing traps with trimedlure as bait for the fly.

Olive fruit fly [31]

Olive fruit fly, Bactrocera oleae (Rossi) is the major pest of commercial olive trees in the Eastern Hemisphere: northern, eastern and southern Africa, Southern Europe, Canary Islands, India, western Asia. The pest is known in California since 1998, originating probably from France. It developed insecticidal resistance to organophosphates. Promising parasitoids attacking olive fruit fly are Psyttalia lounsburyi, P. dacicida, P. concolor, P. ponerophaga, Utetes africanus and Bracon celer. The authors suggest further investigations on parasitoids as control agents for olive fruit fly for different climatic regions.

University of California Pest Management Guidelines [32]

Olive fruit fly larvae feed in olive fruits causing damage. There is zero tolerance for damage on table fruit and about 10% for oil olives. Sanitation is important burying all fruit that are on the ground. GF-120 Fruit Fly Bait, sprays of kaolin clay, and mass trapping are acceptable for use in an organically certified crop.

Ug99 fungus, other crop pests and drought are threatening food security of large population groups

Ug99 has also known as TTKS is a race of black stem rust (Puccinia graminis tritici) which has jumped from eastern Africa and is now infecting wheat in Yemen in the Arabian Peninsula. According to the Food and Agriculture Organization of the United Nations (FAO), countries in the predicted, immediate pathway grow more than 65 million hectares of wheat, accounting for 25 percent of the global wheat harvest. [33]

According to Ravi P. Singh and colleagues 2006 the stem or black rust, caused by Puccinia graminis tritici is of high importance because most wheat cultivars currently grown in its likely migration path, i.e. to North Africa through Arabian Peninsula and then to Middle East and Asia, are highly susceptible to this race. The long-term strategy should focus on rebuilding the "Sr2-complex" to achieve long-term durability. A Global Rust Initiative has been launched to monitor the further migration of this race. [34]


Wheat stem rust fungus Ug99 [35]

The stem rusts are caused by the fungus Puccinia graminis. It affects cereal crops such as wheat. The fungus enters the stems of a wheat plant and destroys the vascular tissue. Ug99 is the most serious pathogen of three cereal rusts. The Ug99 fungus is reddish-brown, and is wind-borne and destroys from 80 percent to 100 per cent of the crops. It is was found in Uganda in 1999 and spread to Kenya, Ethiopia, Sudan, Yemen and Iran.

Four new mutations of Ug99 present a new danger to wheat crops. These new mutations are worrying the Borlaug Global Rust Initiative. The Global Cereal Rust Monitoring System of the FAO say that the new mutations of Ug99 are moving from Africa to Asia, South America, Australia and North America. The new mutations of UG99 evade two stem rust-resistant genes of wheat. Dr. Ravi Singh, says that all new wheat varieties are resistant to both Ug99 and the new races.

Zak Pretorius reports that 47 percent of 129 South African commercial cultivars and advanced breeding lines are susceptible one or both of the new stem rust races.
New breeding lines with high defenses against Ug99 and varieties of stem rust strains are being multiplied and distributed with the financial assistance of USAID in the most threatened areas. The researchers say that the best strategy against the Ug99 race is to replace the susceptible varieties with the new high-yielding, resistant varieties.

Ug99 spreads through East Africa, Yemen, Sudan and Iran and is predicted to proceed to North Africa, Middle East and Asia. [36]

Markers for wheat stem rust resistant genes Sr25 and Sr26 [37]

A new mutation of stem rust agent named TTKSK (syn. Ug99)can evade stem rust resistance genes. The Genes Sr25 and Sr26 transferred into wheat from Thinopyrum ponticum are now used to control this new race and its. DNA markers for Sr25 and Sr26 are needed. The dominant markers Gb for Sr25 and Sr26#43 for Sr26 are known to be valid for eight wheat lines.
Liu and colleagues 2010 tested STS (sequence tagged site) markers amplifying diagnostic bands of Th. ponticum. Marker BF145935 was found to be useful as a co-dominant marker for Sr25, and Multiplex PCR with marker Sr26#43 and 6A-specific marker BE518379 can be used as a co-dominant marker for Sr26.

Cereal rust [38]

The stem, black or cereal rusts are caused by the fungus Puccinia graminis and are a significant disease affecting cereal crops. An epidemic of stem rust on wheat caused by race Ug99 is currently spreading across Africa, Asia and most recently into Middle East and is causing major concern due to the large numbers of people dependent on wheat for sustenance. The strain was named after the country where it was identified (Uganda) and the year of its discovery (1999).It spread to Kenya, then Ethiopia, Sudan and Yemen, and is becoming more virulent as it spreads.

The Ug99 fungus, called stem rust, could wipe out more than 80% of the world's wheat crops as it spreads from Africa, scientists fear. A spore of rust fungus forms a pustule on wheat plants that invades the outer layers of the stalk. The pustule consumes water and nutrients of the plant. It produces reddish-brown flakes on plant stalks. New wheat varieties that are immune to Ug99 must be developed. [39]

Resistance to stem rust gene TTKSK (or Ug99) Rousettksktritmon

According to Rouse and Jin 2011, the race TTKSK (or Ug99) of Puccinia graminis f. sp. tritici possesses virulence to several stem rust resistance genes commonly present in wheat cultivars grown worldwide and new variants were recently detected with even higher virulence spectrum.

Studies on Triticum monococcum have previously detected three resistance genes and introgressed into hexaploid wheat: Sr21, Sr22, and Sr35. The authors detected two genes in Triticum monococcum conferring resistance to race TTKSK that are different from Sr21, Sr22, and Sr35. One of the new genes was effective to all races tested. Further research on these genes may improve protection of wheat against stem rust.

Increasing virulence in Oat Crown Rust cuased by Puccinia coronata [40]

Oat species such as Avena sativa and Avena fatua are menaced by crown rust of oat (Puccinia coronata f. sp. avenae). The strategy to control the disease is based on race-specific seedling genes for resistance.

Carson 2011 warns that the virulence of crown rust fungus population increased from 2001 to 2009. Virulence to Pc38, Pc39, Pc45, Pc48, Pc52, Pc55, Pc56, Pc57, Pc59, Pc62, Pc63, Pc64, Pc68, and Pc96 significantly increased in one or both regions, and no declines in virulence frequency were found. Crown rust resistance Pc genes derived from Avena sterilis and Avena sativa were found to be rapidly defeated. The author calls urgently to surge for new effective resistance sources to Puccinia coronata f. sp. avenae to be introduced to oat cultivars.

Maping oat crown resistance gene [41]

McCartney 2011 describe the Pc91 locust as a highly effective gene against the current Puccinia coronata Corda f. sp. avenae Eriks population in North America. The development of resistant oat varieties. Pc91 is a seedling crown rust resistance gene that is highly effective against the current P. coronata population in North America.

The authors developed DNA markers linked to Pc91 for purposes of marker-assisted selection in oat breeding programs. Pc91 mapped to a linkage group consisting of 44 Diversity Array Technology (DArT) markers. DArTs were transformed to sequence characterized amplified region (SCAR) markers. The authors report that these SCAR markers accurately postulated the Pc91 status of 23 North American oat breeding lines.

Quantitative trait loci Pc 58, PcNQMG/LGCG and OT-27 provide high resistance to oat crown rust [42]

Jackson et al 2010 describe the quantitative trait loci (QTL) in Ogle1040 and TAM O-301,such as Pc58 and PcNQMG/LGCG from the trait TAM O-301 and OT-27 from the trait Ogle1040. According to Jackson and colleagues, the Pc58abc and Pc58a genes were found to be highly effective in two genetic regions responsible for crown rust resistance in TAM O-301, such as the genes Pc58 and PcNQMG/LGCG, and the OT-27 gene in Ogle 1040, provided high levels of resistance to natural races in Texas. The mapping of key loci in OT population may be useful to control crown rust in USA.

Crown rust in forage ryegrasses [43]

Crown rust (Puccinia coronata) is the most important leaf disease in forage and seed crops of ryegrasses (Lolium spp.). Baert J, Ghesquiere A, Vandewalle 2010 evaluated the stability of crown rust resistance of perennial ryegrass Lolium perenne and the Italian Lolium multiflorum qualities. The authors found the crown rust resistance in ryegrass to be durable and consistent over a great part of Europe.

Pathotype specificity in stem rust of perennial ryegrass [44]

Perennial ryegrass (Lolium perenne) is highly heterozygous and heterogeneous, which hampers genetic analysis. To demonstrate the existence of pathotypes for stem rust or other rusts of perennial ryegrass, Pfender 2009 described single-pustule isolates of Puccinia graminis subsp. graminicola, to be applied to a set of genetically diverse individuals of Lolium perenne. The study demonstrates the existence of pathotype specificity in stem rust of Lolium perenne. These informations are useful in breeding for disease resistance.

Fighting crop pests and drought [45]

Dr Lesley Boyd at the John Innes Centre identifies the genetic resistance to stem rust. Stem rust has the potential to wipe out 40-70% of wheat yields and has already caused a painful spike in wheat prices. The Centre says that for farmers who cannot afford to use expensive fungicides, resistance is the only defence.

The centre is also focused on food security for poor rural population developin feasible solutions for crop pests:

Armyworm control

Armyworm (Pseudaletia unipuncta Haworth) may ne controlled with the use of a naturally occurring virus as a biological pesticide. The African armyworm is an insect which feeds on cereal crops.

Witchweed famine threat

Witchweed (Striga asiatica) is a parasitic plant that attacks some of the most important crops such as corn, sorghum, sugar cane, and rice, reducing yields drastically. Witchweed rob nutrients and moisture by tapping directly into the host's root system. Consequently, the host spends energy supporting witchweed growth at its own expense. The Centre is developing resistant crops.

Rice production in Asia will be affected by rising temperatures [46]

Welch et al. 2010 assessed the impact of temperature increases on yield of rice plantations. The authors found that rising temperatures during the past 25 years have already cut the yield by 10-20 percent in several locations and the projected future temperature rise will reduce the rice production even more.

Increasing of minimum temperature during day and higher temperatures during night reduces yield of irrigated farmer-managed rice fields in tropical and subtropical regions of Asia. Increase of temperature during the day may improve growth, but this effect is negatively compensated by increase of minimum temperature and temperatures during the night. A further decline in rice production will mean more people will slip into poverty and hunger, the researchers said. The authors stress that if rice production methods will remain unchanged or new rice strains will not be developed a significant reduction of rice production will be unavoidable during the next few decades.


Rice genes response to increasing temperature [47]

Shiping Wang and his group describe genes associated with response to increasing temperature. They note that these genes are closely related to the disease resistance gene Rice Xa3/Xa26 encoding a leucine-rich repeat (LRR) receptor kinase-type protein against Xanthomonas oryzae pv. Oryzae.

Two orthologs of this family, the NRKe from rice variety Nipponbare and 9RKe from variety 93-11 at the RKe locus, could not mediate resistance to Xanthomonas, but they were transcriptionally induced by raised temperature. Transcriptional activation of NRKe or 9RKe were found to increase plant sensitivity to high temperatures, resulting in spots of dead cells associated with accumulation of superoxides, in different organs.

The authors suggest that the RKe locus is involved in rice response to raised temperature. The LRR domain of RKe protein appears to be important to sense increased temperature. The RKe-involved temperature-related pathway and Xa3/Xa26-mediated disease-resistance pathway may partially overlap.

Disease resistance (R) genes

The authors describe three classes of disease resistance (R) genes: The leucine-rich repeat (LRR), mainly responsible for the recognition of pathogens, which comprises the R genes against Magnaporthe oryzae, which causes rice fungal blast. The second class is the LRR receptor-like R proteins that consist of an extracellular LRR domain and a transmembrane motif, but not found in rice. The last class includes the LRR receptor kinase-like R proteins, which are only found in rice.

The disease-resistance gene

Rice R gene Xa3/Xa26 confers race-specific resistance to Xanthomonas oryzae pv. oryzae that causes bacterial blight. It encodes a LRR receptor kinase-like protein. The Xa3/Xa26 expression is developmentally regulated, plants are susceptible to Xanthomonas strains at the seedling stage but are resistant at the adult stages.

Micro RNAs and plant genome [48]

Tang 2010 defines MicroRNAs (miRNAs) as 21-23 nucleotide (nt) non-coding RNAs that play a key role in regulating the expression of protein-coding genes at post-transcriptional levels in plants and animals. They are located in the intergenic regions of the plant genome.

Tang stresses the importance of co-evolution of the miRNA genes and their target genes which enables the functioning of the gene regulatory network governed by miRNAs in plants. Micro RNAs are involved in negative regulation, but also in positive regulation of most biological processes, and their aberrant expression are linked to diseases like cancer, heart disease and diseases of the nervous system.

Micro RNAs of bees [49]

The micro RNAs in honey bees (Apis mellifera) were studied by Liu et al. 2012, focusing on their association with age-dependent behavioural changes in nurses and foragers. The authors identified 67 novel miRNA, .whereas 9 known miRNAs were significantly different between nurses and foragers, some targeting neural function genes.

Cassava micro RNAs responding Xam infections [50]

MicroRNAs (miRNAs) are active in stress response in plants such as biotic stress caused by a bacterial infection. Patanun et al.2012, report that miRNAs in the Manihot esculenta (cassava) play a role of defence against Xanthomonas axonopodis pv. manihotis (Xam), a pathovar or bacterial strain with different pathogen activity in various other plants.

The authors describe 56 conserved families and 12 novel cassava-specific families, some of which presented increased expression in response to bacterial infection. Some bacteria-repressed miRNAs were found to be involved in copper regulation and target disease resistance genes, similar to miRNAs families of Arabidopsis.

Genetic research on cassava is important because the plant serves as staple food, biofuel, animal feed and industrial raw materials. Patanun et al 2012 identified 169 potential cassava miRNAs belonging to 34 miRNA families and their function were described such as related to drought stress and plant hormone response. [51]


Bacterial leaf blight in rice caused by Xanthomonas oryzae bacterium [52]

Xanthomonas oryzae specie includes the two non-European rice pathogens Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola. It is a species of proteobacteria. The major host of the bacteria is rice.

Host resistance gene, Xa21,from Oryza longistaminata is integrated into the genome of Oryza sativa for the board range resistance of rice blight disease caused by Xanthomonas oryzae pv. Oryzae.

Bacterial leaf blight is the most serious disease of rice in South-East Asia, particularly since the widespread cultivation of dwarf high-yielding cultivars.

Host: The principal host of both pathovars is rice. Oryza sativa subsp. japonica is usually more resistant than subsp. indica to pv. Oryzicola. The bacterium enters by way of hydathodes and wounds on the roots or leaves. Penetration may also occur via stomata, where there will be a resultant build-up of bacteria which subsequently exude onto the leaf surface and re-enter the plant through the hydathodes. Once inside the vascular system, the bacterium multiplies and moves in both directions. Spread takes place in wind and rain, but primarily in flood and irrigation water The bacteria can only move short distances in infected crops. The only means of long-distance dispersal is in infected rice seeds.

Phytosanitary measures: Both Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola are EPPO A1 quarantine pests. EPPO suggests that countries may prohibit import of rice seeds from infested countries. EPPO recommends that seeds should come from a seed-crop subject to growing-season inspection, and should themselves be tested before and after import for the two bacterial pathogens. Use of healthy seed is the best control measure for Bacterial leaf blight in rice.


Seven genes of Xanthomonas oryzae pv. Oryzicola involved in rice disease [53]

Guo et al 2012 identification key virulence factors in Xanthomonas oryzae pv. oryzicola (Xoc). The authors screened Tn5-tagged mutant library of Xoc strain RS105 on rice. Data on bacterial growth and in plant virulence assays suggest that the Xoc genes opgH, purF, thrC, trpA, Xoryp_02235, Xoryp_00885 and Xoryp_22910 are involved in virulence of the bacterium, however, their role in pathogenesis remain unclear.

Novel Gene, hshB, in Xanthomonas oryzae pv. Oryzicola [54]

Virulence factors of Xanthomonas oryzae pv. oryzicola are regulated by a diffusible signal factor (DSF)-dependent quorum-sensing system. Zhao et al 2012 describe the pathogenicity-related gene hshB of Xanthomonas oryzae pv. Oryzicola. The new hshB gene is required for virulence of the bacterium. The hshB transcription is positively regulated by clp gene and DSF, and induced by poor nutrition.

Early defence signalling in rice cells triggered by Xanthomonas oryzae pv oryzae [55]

Grewal, Gupta and Das 2012 describe early defence signalling in rice cells triggered by Xanthomonas oryzae pv oryzae. The authors found major clusters of cell signalling proteins and transcription factors while growth and basal metabolic components were largely found to be down-regulated after inoculation of the pathogen in rice.

As early defence signalling in rice cells, components of the calcium and lipid signalling as well as MAPK cascade were found to be modulated by signals from surface receptors and cytosolic R-proteins. Arose of jasmonic acid, ethylene signalling and abscisic acid was noted. Auxin signalling suppressed in a complex defence response.

Tn5-inserted genes and their contribution to EPS [56]

Zhou et al 2011 studied extracellular polysaccharide-associated (EPS) mutants of Xanthomonas oryzae pv. Oryzicola (Xoc) in relation to Tn5-inserted genes and their contribution to EPS production and virulence in rice. Virulence assays in rice showed that the less EPS production by the mutant, the weaker the virulence in rice. However, those mutants in higher EPS production did not increase virulence significantly in rice compared to that by the wild-type strain. Their data will be useful to understand the pathways for EPS synthesis and the role of EPS-associated genes in Xoc-rice interaction.

To find pathogenesis-related genes of Xanthomonas oryzae pv. oryzicola (Xoc) a Tn5 transposon-mediated mutation library was generated by Zou et al 2011. Twenty-five thousand transformants were produced by using Tn5 transposome and inoculated into rice and tobacco, individually and respectively, for screening candidate virulence genes. The achieved mutant library of Xoc is of high-quality and nearly saturated and candidate virulence mutants provided a strong basis for functional genomics of Xoc. [57]


The European and Mediterranean Plant Protection Organization (EPPO) [58]

The European and Mediterranean Plant Protection Organization (EPPO) is an intergovernmental organisation responsible for European cooperation in plant protection in the European and Mediterranean region. Under the International Plant Protection Convention (IPPC), EPPO is the Regional Plant Protection Organization (RPPO) for Europe.

EPPO's objectives are to protect plants, to develop international strategies against the introduction and spread of dangerous pests and to promote safe and effective control methods. EPPO has developed international standards and recommendations on phytosanitary measures, good plant protection practice and on the assessment of plant protection products (pesticides). It also provides a reporting service of events of phytosanitary concern such as outbreaks and new pest records.

The raised temperature response gene

Two orthologs of the Xa3/Xa26 family NRKe and 9RKe, from two rice varieties, at the RKe locus are involved in rice response to raised temperature. Overexpression of RKe result in the formation of temperature lesion in rice plants
.
The R gene family, like NRKe and 9RKe, provide also other resistances and are a sequence reservoir for evolutionary forces to rapidly generate new R genes, such as the tomato R gene Pto family, the Fen confers sensitivity to fenthion, an organophosphorous insecticide.

Improving pearl millet resistance to drought

Pearl millet provides food security for half a billion people in Africa and Asia. The researchers are improving pearl millet's genetic tolerance to drought caused by climate change.

Fighting root-knot nematodes with fungus

Root-knot nematodes are microscopic worms that feed on plant roots, stunting their growth. The researchers are looking for a natural soil fungus to destroy the worms' eggs.


Reducing arsenic levels in rice

Irrigation with arsenic contaminated groundwater, pollution resulting from mining and the use of municipal solid waste as fertilizer causes rice to have high content of toxic arsenic. Researchers are searching for types of rice which have lower take-up levels of inorganic arsenic.


The Magnaporthe grisea complex, plant pathogenic funguses [59]

Magnaporthe oryzae causes rice blast disease. It is a plant-pathogenic fungus and is member of the Magnaporthe grisea complex which contains at least two biological species that have clear genetic differences and do not interbreed. Magnaporthe oryzae and Magnaporthe grisea are complex members.

The strains isolated from Digitaria have been defined as Magnaporthe grisea, and the isolates from rice were named as Magnaporthe oryzae. Members of the Magnaporthe grisea complex can also infect other agriculturally important cereals including wheat, rye, barley, and pearl millet causing diseases called blast disease or blight disease. Rice blast is the most important disease concerning the rice crop in the world.


Annotation Database for Magnaporthe oryzae cause of rice blast [60]

Kour et al 2012 report the developed an annotation database for Magnaporthe oryzae, the Magnaporthe grisea-Orzya sativa (MGOS) database as a repository for the Magnaporthe oryzae and rice genome sequences

The genome of Magnaporthe oryzae has been sequenced and an automated annotation is available at
http://www.broad.mit.edu/annotation/genome/magnaporthe_grisea/MultiDownloads.html Meng et al 2009 report the Gene Ontology (GO) annotation of Magnaporthe oryzae genome assembly. Proteins received GO term assignment via the homology-based annotation. Literature-based experimental evidence, such as microarray, MPSS, T-DNA insertion mutation, or gene knockout mutation were annotated with new terms developed for Plant-Associated Microbe Gene Ontology (PAMGO). [61]


The rice stripe virus [62]

Rice stripe virus (RSV) is a member of the Tenuivirus genus. It causes chlorotic stripes, chlorosis, moderate stunting and loss of vigour. Severe infections cause the leaves of the plant to develop brown to grey necrotic streaks. If infection is massive the plant dies. The virus occurs in rice, maize, wheat, oat, foxtail millet and wild grasses of the family Gramineae. It does not infect members of other families. The virus is transmitted by Laodelphax striatellus and three other planthopper species. It occurs in rice-growing areas of Asia and Russia, and causes significant reduction in rice yield.

Kim et al 2012 identified 21 potential rice stripe virus resistance factors and explained their association with the host resistance factors within a network model.

Gutiérrez et al 2010 studied the genetics of the African rice Oryza glaberrima MG12 (acc. IRGC103544), compared to Oryza sativa ssp. tropical japonica (cv. Caiapó). The authors found a strong segregation distortion on chromosomes 3 and 6, which suggests the presence of interspecific sterility genes. This may help to overcome hybrid sterility barriers between species of rice. Fourteen loci for plant height, tiller number per plant, panicle length, sterility percentage, 1000-grain weight and grain yield were located by the authors at chromosomes 1, 3, 4, 6 and 9. A locus controlling resistance to the Rice stripe necrosis virus was located between SSR markers RM202-RM26406 (44.5-44.8 cM) on chromosome 11. [63]

In a study of Li et al 2012, it was demonstrated that NS3 gene produce the highest expression in both, rice plants and the virus vector, the small brown planthopper, and disease-specific protein (SP) gene was the only gene with highest expression in rice, but was not present in planthopper. [64]

Zhou et al 2012 introduced a RNAi construct containing coat protein gene (CP) and disease specific protein gene (SP) sequences from rice stripe virus into varieties of rice in varieties of rice. The transgenic plants were strongly resistant to viral infection, and viral replication of SP and CP was significantly inhibited. The authors suggest that the introduction of such a RNAi may reduce the vulnerability of rice varieties to the rice stripe virus. [65]

External abiotic sources of damage of plants

Plant diseases which spread by traffic

Hop mildew was introduced in North America in 1890 coming from Europe and Asia. Hop mildew destroyed the plantations of hop of east and middle west of USA. The mildew mould was found all over the country.
Asparagus rust reached America 1912. Quarantine of plants and seeds being imported are an important measure against uncontrolled spread of plant diseases.

Silage

To avoid moulds and resulting aflatoxins in hay silage and forage as well as silage grains and feeds liquid concentrates of fermentation extracts of Lactobacillus acidophilus, lactis in the pre-bud stage of growth may be added. Alfalfa hay can thus be baled with 18 to 23% moisture.
1 ton square bales hay had the best results on proteins when obtained at 20% moisture.


Most frequent hazards to trees[66]

Beetles

Beetles attack deciduous trees and coniferous forests.If they fed on leaves only the damage is not great, but some beetles such as bark beetles can destroy large parts of the plant beneath the bark. Other beetles transmit virus diseases.


Rhychaenus fragilis

Their larva undermine the leaves of the red beech and copper beech. the leaves turn out brown.


Elm sapwood beetle (Scolytus scolytus)

is known to attack European elms. In America Elms are threatened by Hylurgopinus rufipes


Big brown weevil (Hylobius abietis)

This beetle gnaws round holes in the bark of young conifers causing their death.

Butterflies

If numerous butterflies are present complete defoliation of the growing ends may happen. Of importance are:


Sackbeetle (Thyridopteryx ephemeraeformis)

Male species with wings are harmless.Female species are wingless and live in a sack spun with leaves and leavestalks of USA shrubs and trees. They can cause defoliation of young trees.


Moonbird (Phalera bucephala)

Larvae can cause complete defoliation at various deciduous trees.


Tamarack moth (Coleophora laricella)

The larvae hollow out the needles of tamarack.


Western tent caterpillar (Malacosoma pluvialis:)

Their larvae live on hardwood trees of the Pacific coast of USA, inside of cocoons and nourish themselves with the young shoots of the plants.

Sawflies

Adult species are not harmful, but their larvae destroy leaves and needles heading to complete defoliation.


Larch sawfly (Pristiphora erichsonii)

The larvae nourish from larch needles.causing destructive defoliation.


Willow sawfly (Pontania vesicator)

It forms blister-like galls between the midrib and leave edge of willow trees. In these galls larvae develop.


Plant louse

They are small insects which may have wings or are wingless. attacking deciduous trees and coniferous plants.


Schizoneura lanuginosa

It sucks on elm leaves . not regular galls are formed.

Byrsocrypta ulmi (Byrsocrypta ulmi:)

produces similar lesions as the galls of Schizoneura, but they are club formed.


Pemphigus bursarius

It attacks poplars deforming the petioles with galls.


Sitka spruce

Picea sichensis

It feeds on the vascular system of spruce.


Scale insect

Scale insects are generally covered by a waxlike protective cover. Only female species produce damage. They attack deciduous trees and coniferous plants.and fruits. Leaves and needles may die. Common scale insects are :

San-José-scale Insect, Pernicious scale Diaspidiotus (Quadraspidiotus) perniciosus


Diaspidiotus (Quadraspidiotus) perniciosus

sucks on leaves and fruits of apple-, plums- and peach trees.
The insect is small. it introduces its mouthpieces in the plant and feeds from the liquids. It secrets a white waxi material.
The University of California maintains the Statewide Integrated Pest Management Program, stressing that San Jose Scale has many natural enemies which, however, may be disrupted by broad-spectrum insecticides. Not using broad-spectrum sprays for 2 or 3 years may thus solve San Jose scale problems. [67]


Beech scale (Cryptococcus fagi)

It is a sap feeding insect which together with at least two Nectria fungi causes beech bark disease.
The American Beech (Fagus grandifolia) may be infested with the beech scale (Cryptococcus fagisuga Lind= fagi Baer). The tiny insects attack trunk and branches of the trees suckling sap of the inner bark.White wax covers the bodies of the scale so trees seem to be covered by white wool. Very small wounds caused by the scale enable the Nectria fungus to penetrate the tree killing areas of woody tissue. The tree will be girdled and die. Some infected trees will break off in heavy winds which is called "beech snap".
The scale insect is tiny. It feeds on sap of the inner bark of the tree trunk and branches of American and European beech trees (Fagus sylvatica). The body of the scale is covered by a white wax which gives a look of white wool covering heavy infected parts of the tree. The scale insect causes small wounds and injuries which enables the Nectria fungus(Nectria galligen, Nectria coccinea var.faginata, Nectria ochroleuca) to penetrate the deeper tissues of the tree. leading to widespread damages.
The wind may transport scale insects and fungal spores, spreading the disease. The scale insect and the Nectria fungi can be transported from tree to tree in wind. The Nectria fungi species which are associated to beech bark disease are: Nectria galligena , Nectria coccinea var.faginataand Nectria ochroleuca. Beech scale alone does not kill the trees but after 3 to 6 years an invasion of Nectria fungi takes place which leads to the destruction of the plant.


Oistershell scale, Mussel scale (Lepidosaphes ulmi:)

It feeds from the liquid of plants such as olive and apple trees causing incrustations on branches, twigs and fruits.It also leads to the splitting of the bark.

Moulds of agricultural importance in coffee production

[68] Gibberella xylarioides Heim and Saccas (presumed anamorph, Fusarium xylarioides Steyaert) causes diseases in coffee, cotton plantain and tomato. Countries most affected are Zimbabwe, Republic of Congo (Zaire) and Ethiopia. First symptoms are chlorosis of the leaves which became flaccid and curled. Leaves dry up, turn brown and very fragile, and abscise. The crowns of the dead trees are completely defoliated. Berry blight by Gibberella xylarioides is feared by coffee growers. Internally, in the diseased wood, the main tracheids are heavily infected by mycelium.

Prevention and Control of coffee wilt

Cultivars of Coffea canephora (notably Robusta) which were resistant formed the basis of many of the West African breeding programmes. Coffee lines of Coffea arabica in Ethiopia provided an excellent opportunity to control the disease with resistant varieties. The use of clean seed , frequent inspection of the crop, burning infected material and spraying the soil surface with 2.5% copper (II) sulphate, waiting for at least 6 months after uprooting infected trees reduces the viability of the soil spores, removal bushes between plantations, mantain gaps of a few hundred metres to confine the disease, grafting with resistant varieties are suggested by different authors. The use of chemical pesticides should follow the instructions of national pesticide guide.

The disease had been a serious problem of coffee in several countries in West and East Africa, but was reduced to a relatively minor disease with effective cultural practices and the establishment of breeding programmes in several countries. It was no problem in area under traditional low-management systems, but only reached epidemic proportions where coffee is grown under intensive cultivation. However, the disease is causing considerable losses of Robusta coffee in Zaire and in Uganda.

According to Rutherford 2006, coffee wilt disease caused by Gibberella xylarioides, has been largely contained through the use of host resistance and wide-scale sanitation practices. A reemergence of CWD on Coffea canephora (Robusta coffee) in Uganda, Democratic Republic of Congo, Ethiopia and Tanzania has already led to heavy losses and threatens future production in these countries and elsewhere in the region. [69]

Research and development initiatives by the Regional Coffee Wilt Programme found that wild forest coffee is also susceptible giving rise to concern that it may weaken the genetic base of both Robusta and Arabica genomes. Two fungal strains exist, one infecting Robusta and the other Arabica. The disease can be transmitted from infected wood to adjacent uninfected seedlings. Infected material should therefore be removed from the plantation. The authors recommend to wait at least one year before planting coffee trees at fields infected by the disease. Machete and hoe may spread coffee wilt disease. All Arabica are highly susceptible to the disease and Ethiopian Arabica may present a threat to other countries if it spread. The breeding programmes in Uganda and Tanzania have found Robusta clones which are resistant to the disease. [70]

Control measures adopted by farmers bring coffee wilt to decline in Uganda [71]

Preventive and control measures introduced by farmer of Uganda made coffee wilt disease to declinine. The disease destroyed more than half of older robusta trees in 18 years. Reports show a steady decline or total elimination of the disease in some parts of the country with good agricultural practices. Uganda is the biggest producer of robusta beans. The country approved planting of seven strains of the robusta bean that are resistant to coffee wilt.

Coffee wilt disease in naturally infected Coffea canephora fields at the Coffee Research Institute in Uganda was studied by Musoli et al. 2008. The authors found that an infected tree could infect up to three healthy trees away, in any direction. The rates and levels of epidemic development varied according to host genotypes [72]. Pascal et al 2012 assessed the variability of the resistance against coffee wilt disease in Coffea canephora. The authors a significant genetic variations among the clones and progenies, suggesting a multiple gene inheritable control of the resistance. Selecting tolerant clones for improvement against the disease is therefore indicated. [73]

Genetic groups of Gibberella xylarioides [74]

Gibberella xylarioides, infecting Coffea canephora, is divided in at least three "groups":


Anthracnose fungus (Colletotrichum sp.)

is a disease of plantations of coffee, cashew, melons,citric fruits (Colletotrichum gloeosporioides) but also trees are affected, such as willow trees and poplar trees.Humidity accelerates the growth of the fungus.
Also economical important is Colletitrichum lindemuthianum (Sace and Magn.)which attacks black beans important food in Brazil.


Armillaria mellea

Is a root disease which is a frequent cause of decay of trees in garden and in free nature. It survives as mycelium in the roots and wood of dead trees. The mushrooms of Armillaria grow in clusters at the base of dead or dying tree-trunks or near infected roots.
Plantations of coffee can be infested by Armillaria and Rosselinea spp. which has remained in roots and wood of trees of preceding forest.

Armillaria mellea, a plant pathogen which causes root rot [75]

Armillaria mellea is a fungus which causes the Armillaria root disease. The mushrooms are edible, but it is recommended to cook and discard the water before using the mushrooms in recipes. Intolerances are known. The fungus causes root rot and spreads upwards in to the crowns of infected trees, resulting in dieback of the branches. And death of the plant.

Armillaria mellea

Image Armillaria4a

The fungi live as parasites on living host tissue or as saprophytes on dead woody material. They infect and kill trees that have been already weakened by competition, other pests, or climatic factors. Conifers often respond to infection by producing a copious flow of resin, or callous tissues. Spread occurs when rhizomorphs, growing through the soil, invade roots of the trees. It can be a problem in timber stands, recreation areas, or orchards.

Picture: Armillaria mellea (Honey Armillary) Colony growing on Largeleaf Linden in Vieira do Minho, Portugal. Picture source: Júlio Rei, at Wikipedia: Armillaria mellea Image Armillaria3

U.S. Department of Agriculture Forest Service recommendations on Armillaria management[76]

The eradication of Armillaria root disease is not feasible. All strategies management should be focussed on limiting disease buildup or reducing its impact.
Chemical fumigation: Fumigation using chloropicrin, methyl bromide, and carbon disulfide, can reduce the infection level to protect high value trees.
Cultural management: Cultural management in commercial forests includes: (1) reforesting stands with a mixture of species ecologically suited to the site and not obviously infected by Armillaria; (2) maintaining vigorous tree growth without causing undue damage to soils; (3) minimizing stress to and wounding of crop trees; and (4) reducing the food source by uprooting infected or susceptible root systems and stumps. Sometimes other pests or stand conditions may be more significant than Armillaria, and pest activity, site and stand characteristics should be considered.

Image Armillaria8
Picture: Leaves of Laburnum tree (left) and young apple tree (right) damaged by Armillaria.

Grapevine root rot by Armillaria mellea [77]

Peradzzolli et al 2010 identified 24 genes that were upregulated in grapevine roots after Armillaria. mellea challenge. These genes encoded protease inhibitors, thaumatins, glutathione S-transferase, and aminocyclopropane carboxylate oxidase, as well as phase-change related, tumor-related, and proline-rich proteins, and gene markers of the ethylene and jasmonate signaling pathway. According to the authors, in vitro experiments suggest that phase-change-related protein plays an important role in the defence response of grapevine roots against Armillaria mellea.

Static piles of ground green waste are source of plant pathogens [78]

Downer et al 2011 recommend to turn intermittently green waste stockpiles contents to move pathogen within the pile and can thus be killed by heat, microbes or chemical degradation. The authors report that sclerotia-forming pathogens pose the greatest risk to survive. Ground green waste were found to be more effective than aged green stock piles because of the temperature which rises up to 70° with fresh ground green waste, but remains low by 40° with aged green waste. Sclerotinia sclerotiorum was the most resistant pathogen in both types of unturned stock piles, and their propagules are expected to survive 363 days. Other plant pathogens like Phytophthora cinnamomi, Armillaria mellea, and Tylenchulus semipenetrans were less resistant to the environment of stock piles.


Fruit tree red spider mite

Mites are spider like organisms which nourish from plant sap.
Economical important mite is the Fruit tree red mite Metatetranychus ulmi. it feeds by sucking the underside of leaves of vine and fruit trees like apple, pear, cherry-trees. The leaves turn brown and dry.


Bursaphelenchus xylophilus

It is a nemathode which attacks pines. Its habitat is the southwest Asia and is present in USA, Japan China and Scandinavia. The nemathode is vectored from one pine to another by cerambycid loghorn beetles, also known as sawyers of the genus Monochamus. It can destroy 50 to 70 years old trees within few years.
In Germany,Saxony living nematodes Bursaphelenchus xylophilus were found for the first time among pallet wood of Chinese origin. As wood for pallets are of poor quality of dead trees are used pallets turn out to become a way of spread pests all over the world.


Diseases of potatoes

Tuber diseases

Pink rot

is caused by the fungus Phytophthora erythroseptica which is soil-borne. Pink rot can be detected by a smell of ammonia prior of visual symptoms.


Phytium leak

is caused by the fungi Phytium debaryanum and Phytium ultimum.Also known as water rot is caused by the fungus Phytium spp. living in the soil. The fungus invades the tubers through wounds made during harvest. It causes internal wet spongy rot with hollow cavities leaving behind only the tuber shells as thin paper skins.
Avoid overwatering near harvest. Avoid unnecessary damage to the tubers during harvest.


Fusariun dry rot

It is a postharvest disease of potatoes. It is caused by several soilborne fungus Fusarium. Infected tubers have wrinkled, sunken, brown to black lesions. The Fusarium fungi are common in soil and decaying plants as resistant spores. After low-temperature storage, internal tissues become firm and dry or even powdery.


Potato bacterial ring rot

is caused by Clavibacter michiganensis subsp. sepedonicus producing yellow areas which start on leave margins later turning brown. The leaves look like being burned.
Brown necrosis of the tubers are formed from the middle of the tuber, progressing to surface, leaving sometimes only hollow shells.


Rhizoctonia Canker

It is a disease of potatoes caused by the fungus Rhizoctonia solani. It is known as black scurf Hard black bodies called sclerotia are formed on the surface of the tubers. Delayed budding is caused by an attack of the buds by the fungus. Misshappen stems and weak plants with brown cankers at the base and belowground portions of the stem.


Silver scurf

Is a potato disease caused by the fungus Helmithosporium solani. It causes a metallic discoloration of the epiderma and causes weight loss during storage due to increased water loss of the tubers. Shrinking and flabbiness affects peeling of the tubers reducing consumer acceptance and rejection. It is a seed-borne disease.


Spongospora, Powdery Scale

Is a disease of potatoes caused by Spongospora subterranea which can be the vector of the mop-top furovirus.

Net necrosis

Foliar diseases


Early blight

Potato early blight is caused by the fungus Alternaria solani. It is a disease of stressed and senescing plants. Lesions of the leaves are circular with a target look. They turn out yellow and drop. Tubers develop dry rot lesions which appear sunken.
Infection is possible during wet and warm weather conditions (dew, rain or sprinkler irrigation). Tubers can be contaminated by lifting them through the surface soil.
Early blight can be reduced with with optimum growing conditions like fertilization,irrigation and other pest controls in order to strengthen the plants. Fungicide application is recommended only when the plants become diseased in a very early stage so the damage will be considerable.


Potato late blight [79]

Potato blight is caused by Phytophthora infestans a fungus-like organism whose sporangia are dispersed by wind. To avoid damage caused by blight the potato farmers watch weather forecasts for the climatic conditions which favor the spread of the disease. Spraying fungicides may be unnecessary when blight spores are not present in the air current. More efforts are being done to control spore flight with air sampler in connection with flow cytometer. Particles collected by the sampler are stained and analyzed in the cytometer using laser light. Airborne potato blight spores are identified and counted against a background of other fungal spores, pollen and inert particles. This system is being developed by Dr. Gareth Griffith of the Institute of Biological Sciences at the University of Wales, Aberystwyth. The forecast of the potato blight disease which has caused the Irish Potato Famine, 1845-1847 leading to the death of 1 million people could be improved using data of the climatic forecast ( suitable conditions for pathogen growth) and detection of the sporangia in air (inoculum). With the help of these data the decision to spray the crops could could reduce excessive fungicides.

Potato late blight is caused by the fungus Phytophthora infestans and is the most important potato disease. Specially the US-8 genotype is strongly resistant to the fungicide mefenoxam and is together with the genotype US-11 very aggressive.
The spores of the fungi are carried by wind or other infection ways from one field to another. Once the fungi is established in the plant no chemical fungicide can kill it. Prevention is therefore the best way to prevent great damage. Fungicides must always be applied before the crop shows any signs of infection. The fungus hibernates in infected potato tubers as mycelium.New sprouts of the mycelium invades the cortical tissue of the tubers.Reaching the aerial part of the plant sporangiosphores will be created and which emerge through the stomata of leaves or stems.The sporangia which are then produced can infect other wet plants by means of wind and rain. Infection of tubers may not be seen during harvest, but it will go on during storage.
The sporangia can also spread on soil and tubers near the surface.
Prevention of potato late blight depends on the forecast of temperature and humidity of the specific region
When the relative humidity is below 80% the sporangia will lose its ability to germinate in 3 to 6 hours. Free moisture or dew makes germination possible.Best conditions for growth of the fungus is 100% of relative humidity.
Preventive application of fungicides are necessary if the environmental conditions are favorable for the disease. Mefenoxam is not recommended because Phytophthora infestans is resistant to it. If there is an infection of late blight the vines should be dead 2 to 3 weeks before harvest to avoid contamination of the tubers, as Phytophthora infestans does not survive for long in dead foliage.

Copper free compounds had either no or limited effects on blight compared with copper fungicides [80]

The EU project leaded by Professor Carlo Leifert aims the development of management of late blight in EU organic potato production. In this project it is being notet that there is a widespread view that a copper fungicide ban will have serious consequences for organic potato production unless effective alternatives are available.

Some conclusions of this project were:
Extracts of manure-based composts gave control of blight in potato leaf assays but not in the field. However, use of an adjuvant in combination with an autoclaved compost extract gave improved control and slightly higher yields in an experiment in 2003. Some micro-organisms, plant extracts and existing products showed promising effects on blight control. Efficacy of a range of commercial and novel anti-fungal compounds was unaffected by dose rate or formulation. Copper free compounds had either no or limited effects on blight compared with standard copper fungicides at normal rates but low doses of copper products were almost as effective.

Late blight disease affecting U.S. Northeast tomatoes and potatoes [81]

The University of Cornell warns for late blight, caused by Phytophthora infestans affecting tomato and potato around the world. The New Jersey Agricultural Experiment Station of the Cornell University stresses that the 2009 cool summer with frequent rains, weather have facilitated late blight development in the Northeast of the U.S.A.

According to the report commercial growers spray fungicides to prevent its spread, however many homeowners are not aware of the disease. Their affected plants provide spores for their neighbor's gardens and for commercial farms. The disease is reported over a broad area of the Northeast. Infected plants have been distributed to large local retail stores from Ohio to Maine, facilitating the dissemination of the disease.

Spraying regularly with fungicides based on chlorothalonil is being recommended.. The symptoms develop on tomato leaves, stems and fruit. The leaf lesions are water-soaked when exposed to watering or heavy overnight dews. White fungal growth may appear at the affected parts of the plant. Other plants related to tomatoes and potatoes, such as petunias are also at risk of the disease.

Downy mildew of basil [82]

Downy mildew of basil was reported at farms in the northeast USA in 2008. Yellowing of the plant were often attributed to nutritional problems, therefore the disease was often ignored.

The basil downy mildew pathogen can be spread in contaminated seed, in infected basil leaves, and as wind-dispersed spores. Downy mildew also was observed recently on ornamental plants related to basil, in particular coleus and salvia. These plants all belong to the Lamiaceae family, which includes basils, mints, sages and other aromatics. Contaminated seed is most likely the way that the basil downy mildew pathogen has been able to move between geographically-separated areas.

Phosphorous acid fungicides, ProPhyt and K-Phite and Actinovate AG are being recommended to control downy mildew on herbs.


Net necrosis and Potato leaf roll virus

Net necrosis is caused by the potato leaf roll virus (PLRV). It is a damage of the cells of the vascular tissue.of the tuber causing specific symptoms.
The virus can be spread by means of various aphid species such as the green peach aphid which can be killed with carbamate insecticides. Mechanical contact does not cause a transmission of the virus from plant to plant. It occurs only with a vector such as the aphids.

Aphids survey to predict responses to environmental changes [83]

According to Dr Richard Harrington aphids, such as the peach-potato aphid (Myzus persicae) are found flying around almost four weeks earlier, and their number in spring and early summer is increased when crops are particularly vulnerable to damage.

Aphids extract large amounts of sap, weakening the host plant, and spread plant viruses. Aphids excrete very sticky honeydew, which can encourage the growth of moulds causing further weakening and attract ants which live in symbiosis with the aphids.

Up to date news on the distribution and abundance of pest aphids at a regional scale in UK based on data from a network of sixteen suction traps are provided by the Centre for Bioenergy and Climate Change Department of Plant and Invertebrate Ecology, Rothamsted Research. These long-term data on the

seasonal appearance of flying aphids not only show that there are already noticeable changes in the UK climate, but they also provide the knowledge which will help to mitigate the consequences. [84]

Richard Harrington and colleagues 2007 suggested the possible value of aphids in predicting responses to environmental changes. Aphids have a short generation time and low developmental threshold temperatures and respond particularly strongly to environmental changes. Forty years daily survey data of aphids have been collected throughout the European Network "EXAMINE". [85] [86]

Cereal aphids

The Russian wheat aphid (Diuraphis noxia) cause significant losses in cereal crops and is considered to be the most devastating pest of bread wheat, durum wheat and barley. The saliva of this aphid is toxic to the plant and causes whitish striping on cereal leaves. Feeding by this aphid will also cause the flag leaf to turn white and curl around the head causing incomplete head emergence. Host plants are cereal grain crops including wheat and barley and to a lesser extent, wild grasses such as wheatgrasses, brome-grasses or ryegrasses.

Aphid strains [87]

The Russian wheat aphid biotype designations of seven biotypes 1-7 (RWA1-7) was confirmed by Randolph and colleagues 2009. RWA 1 was found to be the least virulent of the aphids tested. RWA 3 was highly virulent and RWA 2 was the most virulent strain of all aphids.

Aphids multiple invasion in USA [88]

Even after several aphid resistance genes had been introduced in commercial wheat and barley genotypes up to eight virulent biotypes occur across the western United States. Using genetic maping techniques Liu and colleagues 2010 found that there have been at least two Diruaphis noxia invasions of different origin into North America which resulted in postinvasion diversification giving origin to the actual biotypes.

Symbiosis between aphids and the bacterium Buchnera aphidicola [89]

Swanevelder and colleagues 2010 describe the symbiosis of the Russian wheat aphid (Diuraphis noxia) with the bacteria Buchnera aphidicola. This symbiosis turns the aphid able to feed on phloem which lacks of several essential aminoacids which are synthesized by the Buchnera aphidicola. The authors found pseudogenes, which are genes that have lost their protein-coding ability, and lower plasmid copy numbers of essential amino acid genes. The symbiosis between both species seems to degenerate. Other genetic sequences, however point to the fact that the symbiosis between Buchnera aphidicola and aphids is still valid for a variety of hosts, conclude the authors.

Oxylipin-based aphid defence mechanism of Dnx gene in wheat [90]

Smith and colleagues 2010 report that plants containing the Dnx resistance gene upregulated more than 180 genes related to reactive oxygen species, signaling, pathogen defense, and arthropod chemical and physical defense, when challenged by Russian wheat aphid (Diuraphis noxia). Based on their researches, the authors suggest that the Dnx Russian wheat aphid is regulated via the oxylipin pathway.

Greenbug Schizaphis graminum biotypes [91]

According to a study of Weng and colleagues 20101 marker data of the cereal aphid pest greenbug, Schizaphis graminum, revealed host-adapted genetic divergence as well as regional differentiation. Host associated biotypic variation was found at agricultural cultivated areas, and more geographic divergence was found in populations living on noncultivated grasses. Monitoring of greenbug biotyping variation on crop plants and noncultivated grasses may be useful to detect new virulent biotypes of the greenbug.

Host plant resistance to aphids [92]

Dogimont and colleagues 2010 report that resistant-breaking biotypes have occurred due to a limited number of aphid resistance genes and alleles in host plants. Two aphid resistance genes encode NBS-LRR proteins involved in plant resistance to aphids.

Aphids prefer to settle on fertilised plants [93]

Aphid species (Uroleucon tanaceti and Macrosiphoniella tanacetaria) prefer to settle on plants (tansy) fertilised with ammonium nitrate. The phloem sap of these plants contained higher amino acid concentrations, without a change in the proportion of essential amino acids. The aphids presented a longer phloem feeding time on fertilised plants and also a longer stay in sieve tubes, compared with plants which were not fertilised.

Nowac and Komor 2010, authors of the study, say that aphids identified the nutritional quality of the host plant mainly by the amino acid concentration of phloem sap, not by leaf surface cues nor the proportion of essential amino acids. The authors note that Uroleucon tanaceti infestation increased the methionine plus tryptophan content in phloem significantly. This alters the nutrients of the plantmanipulating the plants nutritional quality, and causing premature leaf ageing.

No significant change in feeding behaviours of aphids living on low amino acid phloem concentration [94]

The amino acid permease gene AAP6 (At5g49630) regulates phloem amino acid composition. Abolished function of this gene in Arabidopsis thaliana produced phloem with low total amino acids and low levels of lysine, phenylalanine, leucine, and aspartic acid. However, despite these changes in diet, Myzus persicae aphids presented only small changes in feeding behaviour on this host.

AKR gene is related to resistance to aphids [95]

The authors found that resistance to bluegreen aphid (Acyrthosiphon kondoi) was related to AKR, a single dominant gene which was also found in cases of resistance to pea aphid (Acyrthosiphon pisum). Studies were performed with a clover-like plant Medicago truncatula presenting similar transcription factor expression patterns.

Ilarviruses, agronomically relevant viruses

The viruses of genus Ilarvirus are of agronomic importance causing worldwide economic losses in yield and fruit quality affecting mainly Prunus spp. Ilarvirus genus is a member of the family of the Bromoviridae.

Pallas et al. 2012 point to the fact that Ilarviruses and Alfalfa mosaic virus require only few molecules of the coat protein in the inoculum in order to be infectious. This is known as genome activation. Four ilarviruses, Prunus necrotic ringspot virus, Prune dwarf virus, Apple mosaic virus, and American plum line pattern virus, are important pathogens of all important fruit trees. [96]

The genome of Ilarviruses is segmented, tripartite linear ssRNA(+) genome composed of RNA1, RNA2, RNA3. Each genomic segment has a 3' tRNA-like structure and a 5'cap. [97] Ilarvirus: According to the NCBI taxonomy database The genus Ilarvirus is divided in 6 subgroups. [98]

Blackberry chlorotic ringspot virus [99]

Blackberry chlorotic ringspot virus (BCRV) is an ilarvirus infecting blackberry, rose and raspberry. Herbaceous hosts and seed transmission such as Rosa multiflora seeds are efficient transmission modes of ilarviruses.

Blueberry shock virus [100]

Blueberry shock virus (BSIV) infection causes, bushes infected during bloom loss of foliage and blossoms resulting in yield loss. Shock virus is pollen borne and is transmitted by pollinators between plants.


Ilarvirus subgroup 1

Parietaria mottle virus (PMoV) [101]

Parietaria mottle virus (PMoV) infection occurs at the edge of tomato and pepper crops in the north of Spain. The virus may be present in pollen from Parietaria officinalis plants (a perenial herb of the Nettle family-Urticaceae) and transmitted by insects to tomato and pepper. Aramburu et al. 2010 suggest to eradicate infected P. officinalis plants that surround tomato and pepper crops to restrain virus spread.

Bacopa chlorosis virus (BaCV) [102]

The complete genome of Bacopa chlorosis virus is described by Menzel et al. 2012. The virus caused chlorosis in Impatiens in Germany. It had been unknown to occur outside the US. It has high identity to parts of the genome of Parietaria mottle virus. It can invade important flowering plant and pose a risk for the horticultural industry, warn the authors.

Tobacco streak virus [103]

Tobacco streak virus is a pathogen of soybean in Brazil and the US. Soybean strains resistant to tobacco streak virus should be tested under temperatures of 32°C which may turn these strains susceptible to at these temperatures, write Hobbs et al. 2010.

Strawberry necrotic shock virus [104]

Blackberry chlorotic ringspot (BCRV), strawberry necrotic shock (SNSV), and tobacco streak viruses (TSV), may infect Rubus and Fragaria species. According to Tzanetakis et al. 2010 all three present genomic similarities and cause symptoms previously attributed to infection by TSV alone.

Sunflower necrosis virus disease [105]

Sunflower necrosis virus disease causes a high damage to sunflower production in India. Srinivasan and Mathivanan report the biological control of sunflower necrosis disease. The authors used with a plant growth promoting microbial consortia consisting of strains of Bacillus licheniformis, Bacillus sp., Pseudomonas aeruginosa and Streptomyces fradiae in liquid formulation obtaining 51% of reduction of sunflower necrosis treatment also improved the seed germination.


Grapevine angular mosaic disease Girgis94729

The attack of the virus is reported by Sobhi et al 209 to result in sharp angular mosaic on leaves, along the veins and in vein angles, malformations, abortive flowers or very few berries with smaller, wrinkled and non-germinating seeds. Based on its symptomatology and serology it was classified as a novel virus designated as Grapevine angular mosaic virus (GAMV) (Girgis et al. 2000; Girgis 2002).

Ilarvirus subgroup 2

Asparagus virus

Asparagus viruses I and II produce severe reduction of vigour asparagus plants under attack of both viruses together, susceptibility to Fusarium wilt is increased. A single attack, however, results in only reduced signals of the disease. Both viruses are transmitted by aphids. Asparagus virus II is also transmitted through seed, by pollen and may be transmitted mechanically by farming activities. [106]

Citrus leaf rugose virus [107]

The citrus-leaf-rugose virus (CLRV) is a mechanically transmitted citrus virus, first discovered in Florida. It was transmitted to numerous citrus and herbaceous hosts. Symptoms differ from alterations caused by citrus variegation virus.

Citrus variegation virus [108]

New citrus groves in Cyprus remained citrus variegation virus free as a result of 1957 quarantine regulations and the Citrus Certification Programme of 1998. However, older groves of Valencia, Jaffa, grapefruit, Clementine trees are infected with several viruses, including the citrus variegation virus. Moreira reports the presence of citrus variegation virus in old sweet lime trees (Citrus limettioides Tan.) used as coffeshade in Costa Rica. The virus was identical to the virus infecting trees or Riverside in California. [109]

Elm mottle virus [110]

Elm mottle virus causes white mosaic or chlorotic ringspots in mechanically inoculated Forsythia intermedia and Syringa vulgaris, and ringspot and line-pattern leaf symptoms in elm.

Hydrangea mosaic virus [111]

Thomas et al 1983 describe the hydrangea mosaic virus (HydMV) isolated from Hydrangea macrophylla presenting chlorotic mosaic leaf symptoms. It was seed, but not aphid transmitted.
The best tests for diagnosis of Hydragea mosaic virus are in Hydrangea, leaf symptoms differ from the malformations, ringspots or chlorosis caused by Hydrangea ringspot virus, cucumber mosaic, tobacco ringspot, tomato ringspot, tomato black ring, Arabis mosaic or tobacco rattle viruses. Virion instability, shape and small numbers in leaves is characteristic. [112]

Spinach latent virus

The genome of spinach latent virus (SpLV) was compared with that of the citrus leaf rugose virus-CiLRV, also a member of the genus Ilarvirus. There are marked differences between the RNA 3, however RNAs 1 and 2 are similar. However, the putative 2a protein of spinach latent virus contains a C2H2 type "zinc finger"-like motif located towards the carboxy terminal of the protein which is absent other members of the family Bromoviridae. [113]

The virus may become important for the tomato industry because of high frequency of seed transmission in many plant species, being already reported in tomato plantations in New Zealand.. SpLV has never been detected in other submitted tomato samples. Consequently, SpLV is not considered to be established in New Zealand. [114]

Tulare apple mosaic virus [115]

Tulare apple mosaic virus caused severe mosaic disease of apple, similar to those caused by common apple mosaic. The virus was found only once in nature, in one apple tree in Tulare County, California. The virus exists only in experimental material.

Ilarvirus subgroup 3

Apple mosaic virus [116]

Apple mosaic virus is widespread in apple plantations. The virus also affects plum and rose and is related to Prunus necrotic ringspot virus. It produces pale to bright cream spots which become necrotic when exposed to sunshine and heat. 'Golden Delicious and Jonathan are most affected varieties, bud set may be compromised.

Humulus japonicus latent virus [117]

Humulus japonicus latent virus (HJLV) was isolated in UK from two plants of Humulus japonicus grown from seed from China. The virus was placed in subgroup 3 because of its serotype similar to the group. This virus has not been found again.

Prunus necrotic ringspot virus [118]

Some variants of prunus necrotic ringspot virus (PNRSV) do not produce symptoms in plants. Other variants produce necrotic spots and shot holes on young leaves during the first year of systemic infection, which do not show in later years. Other variants produce necrotic reactions, chronic chlorotic leaf mottle and necrosis, leaf enation (an outgrowth from the surface of the leaf), deformity, delayed fruit maturity, and fruit-marking symptoms.

Ilarvirus subgroup 4

Fragaria chiloensis latent virus [119]

Fragaria chiloensis latent virus is a virus of strawberries of South America. Tzanetakis and Martin 2005 propose the name Fragaria chiloensis cryptic virus. The authors found that the polymerase region was encoded by a dsRNA species of approximately 1.8 kb, which is similar in size to the genomic molecules of other cryptic viruses that encode the virus polymerase which supports the proposed name.

Prune dwarf virus [120]

Prune dwarf virus causes dwarfism of leaves on certain prune and plum plants, and yellows in sour cherry. The sequence of prune dwarf ilarvirus (PDV) RNA-1 and its single ORF are typical for the Bromoviridae family. The virus is borne in pollen and seed. Seed is responsible for 80

Ilarvirus subgroup 5

American plum line pattern virus [121]

American plum line pattern virus (APLPV) is serologically distinct from other viruses which cause line pattern symptoms. In Europe, line pattern in plum is caused by strains of prunus necrotic ringspot ilarvirus or apple mosaic ilarvirus. In the western USA also, plum line pattern is caused by a strain of prunus necrotic ringspot ilarvirus. In fact, line pattern symptoms have been reported from many other areas of the world, such as New Zealand and India, but there are no indications by which virus they are caused. Such symptoms as apricot line pattern or peach line pattern could conceivably be caused by any of these viruses.

Ilarvirus subgroup 6

Lilac ring mottle virus [122]

Lilac ring mottle virus causes rings and line patterns on lilac (Syringa vulgaris). Transmission to various herbaceous hosts may happen mecannicaly, and is seed-borne in three of them. According to Van Der Meer et al. 1976 inactivation occurs in crude sap in 10 min at 63-65°C, after dilution to 10-4 and after storage for 5 h at 20°C.

Scott and Ge 1995 describe the nucleotide sequence of lilac ring mottle ilarvirus RNA 3' terminal structure with similarieties to apple mosaic ilarvirus (ApMV), however, it shows greatest identity with citrus leaf rugose (CiLRV) and citrus variegation (CVV) ilarviruses, which are of subgroup 2 of the genus. It is therefore being proposed by Scott and Xin Ge to assign it to the subgroup 2. [123]

Lilac leaf chlorosis virus (LLCV) [124]

Analysis of the nucleotide sequence of the RNA 1 of lilac leaf chlorosis virus (LLCV) supports a close relationship with subgroup 3 ilarviruses according to James and Varga 2012.

Potato yellowing alfamovirus virus (PYV) [125]

Potato yellowing virus (PYV) has been found in field samples of potato from Peru, at different localities, with up to 88% infection of the samples. PYV causes yellowing symptoms on some potato cultivars and can thus be presumed to be harmful. However, there is no specific information on effects on yield. On artificial hosts, the symptoms it causes are often less severe than those caused by Alfalfa mosaic alfamovirus (AMV).

PYV has recently been added to the set of non-European potato viruses of the EPPO A1 quarantine list (OEPP/EPPO, 1984a). In general all regional plant protection organizations outside South America recommend very strict measures for potato material from that continent. There is a great risk of introduction due to the increased international exchange of breeding material and germplasm, whether in the form of tubers, rooted cuttings, in vitro cultures or true seeds.


Raphanus latent virus [126]

Schmelzer 1976 reports a mosaic disease was stated in seed plants of garden radish in Germany. It spreaded infecting cent of the stand. Cauliflower mosaic virus was isolated from seeds. It was the first report of a spontaneous virus infection of Raphanus sativus var. sativus in Europe.


Tomato necrotic spot virus [127]

Batuman et al. (2009) describe a virus-like necrosis symptoms, most similar to those induced by Tobacco streak virus (TSV), in tomato plants in the Central Valley of California. Causative agent was a new ilarvirus species named tomato necrotic spot virus. The mode of transmission is unknown, but it may involve thrips feeding on infected pollen, a known method of transmission for TSV, write the authors.

Viola white distortion virus [128]

Viola white distortion virus, a new ilarvirus species causing a severe disease on viola plants in northern Italy. Ciuffo and Turina submitted the Viola white distortion virus isolate Vl9 movement protein gene, complete cds on december 2009.

Phenology

Phenology is the study of the annual cycles of plant and animals and how they respond to seasonal changes in their environment. The uses of phrenology can be used in IPM:


Desertification [129]

On the occasion of the World Day to Combat Desertification to be celebrated on June 17, 21006, worldwide farmers of the International Federation of Agricultural Producers presented a message, highlighting the essential role of farmers to combat desertification and their commitment to join efforts along with the international community and other relevant stakeholders to be more effective in this endeavour:
In a new policy statement, IFAP calls for increased investment in agriculture to turn dryland areas into economic ones through: investments in family farming and local food security which are the engines of economic growth; looking at all the assets of rural development; as well as development of people centered and rights based approaches to rural development.

Natural resources such as fertile topsoil, organic matter, plant cover and healthy crops are the most severely affected by desertification.

The United Nations Convention to Combat Desertification (UNCCD) presents a sustainable development and poverty reduction instrument. Unfortunately lack of investment for implementing the Convention due to a lack of political will and commitment hinders its activities. [130]

Almost one-quarter of the earths land surface are defined as 'desert' , being home for over 500 million people. Degradation of fragile drylands are progressing due to overgrazing, overuse of land climate variations deforestation and poor irrigation methods.

Most of the 12 desert regions have a rainfall forecast of 10 to 20 per cent lower by the end of the century. Very threatened by drought are Chad, Iraq, Niger and Syria.

Soybean diseases

The Brazilian Census Bureau (IBGE) estimates an harvest of 59.2 million tonnes of soybeans in 2005-06, up from 51.1 million tonnes in 2004-05. Some crop losses due to dry weather in the previous season were reported.

Asian rust is another factor that could endanger some part of the Brazilian crop. Small and medium-sized farmers cannot pay the spray if rust attacks. Asian soybean rust was first found in Brazil in 2002 and has since spread to Brazil's major soy regions.

Extreme heat and drought in much of the Midwest in 2005 limited the spread of soybean rust to the southern United States (central Florida, reaching Kentucky and Texas ).X. B. Yang of the Department of Plant Pathology of the Iowa State University the disease developed slower in kudzu plants in southern states compared with those in South America. This might have been due to the biology of the U.S. Kudzu soy plant. However, the disease is still a serious threat to all U.S. soybean growing areas. [131]

Asian soybean rust

It is a fungal disease caused by Phakopsora pachyrhizi. It can defoliate plants and reduce pod set, pod fill, seed quality and yield.

Similar looking diseases

Diseases which are similar looking to asian soybean rust are: [132]

Extreme heat and drought in some regions of Europe

The European Commission in a statement comments heat and drought in summer 2006 as follows:
"Frequent and persistent heat waves associated with dry conditions characterised the whole month of July. At the same time, the drought and the heat stress phenomena moved northward through the continent affecting particularly those areas where the winter crops were still at their sensitive stage (ripening/maturity),

Both in southern and in northern Europe, the spring-summer crops, in full vegetative to flowering phase, were suffering from the above-mentioned conditions. All this also had an impact on water reservoirs, reducing the irrigation resources mainly for grain maize, sugar beet and potatoes.

Image Corn Severe drought in German corn

Summer 2006 a severe drought makes corn leaves acquire a curly formate.

Genetic diversity within a species improves the ecosystem

[133] [134] Gregory Crutsinger and colleagues from the University of Tennessee in Knoxville found that increasing population genotypic diversity in a dominant old-field plant species, goldenrod (Solidago altissima), determined arthropod diversity and community structure and increased aboveground net primary productivity (ANPP), such as the insect diversity.
Image flowers Goldenrod (Solidago altissima)

The scientists counted and identified every insect on every plant. Crutsinger found that plants from plots that had the most genetic diversity ,12 genotypes, were bigger and contained not only the most insects but also the most species of insects. than plots with a single plant genotype.

The results of the study suggests that the goldenrods in the genetically diverse plots had provided better quality resources to the insects, with a resulting positive impact on the plants too.

Crutzinger thinks that tiny differences in plant characteristics, from leaf shape to stem thickness, might have promoted a wider diversity of pests and pollinators and spread out their effects over the plot, so that some plants are really nailed by insects and some are barely touched at all, The plants might also have picked nutrients out of the soil differently from each other, helping them make best use of the resources available.

Crutsinger concludes that the findings are significant for conservation biology and stresses the importance of genetic diversity within the crops.

Similar results had been reported by Youyong Zhu [135]. He mixed a disease-susceptible with a disease-resistant variety of rice. Growing the two together boosted yields. Youyong Zhu concluded that crop heterogeneity is a possible solution to the vulnerability of monocultured crops to disease. Both theory and observation indicate that genetic heterogeneity provides greater disease suppression when used over large areas.

Insect Resistance Management

[136] Insect resistance management (IRM) is the term used to describe practices aimed at reducing the potential for insect pests to become resistant to a pesticide. Bt IRM is of great importance because of the threat insect resistance poses to the future use of Bt plant-pesticides and Bt technology as a whole. Specific IRM strategies, such as the high dose/structured refuge strategy, will mitigate insect resistance to specific Bt proteins produced in corn, cotton, and potatoes.

Academic scientists, public interest groups, organic and other farmers have expressed concern that the widespread planting of these genetically transformed plants will hasten the development of resistance to pesticidal Bt endotoxins. Effective insect resistance management can reduce the risk of resistance development.

The insect resistance management section provides EPA's scientific assessment of various Bt plant-pesticide IRM strategies by reviewing the data and information available to the Agency. The Agency will use this assessment, the report of the FIFRA SAP meeting on October 18, 2000, and all public comments in its development of its risk management decisions for Bt plant- pesticides. The whole document can be downloaded at http://www.epa.gov/oscpmont/sap/meetings/2000/october/brad4_irm.pdf

Insect pest discussed in the EPA insect resistance management documet are:

Common Name Scientific Name Crop
Black Cutworm Agrotis ipsilon (Hufnagel) corn
Cotton Bollworm Helicoverpa zea (Boddie) cotton
Corn Ear Worm Helicoverpa zea (Boddie) corn
Colorado Potato Beetle Leptinotarsa decemlineata (Say) potato
Common Stalk Borer Papaipema nebris (Guen.) corn
European Corn Borer Ostrinia nubilalis (Huebner) corn
Fall Armyworm Spodoptera frugiperda (J. E. Smith) corn
Pink Bollworm Pectinophora gossypiella (Saunders) cotton
Southern Corn Stalk Borer Diatraea crambidoides (Grote) corn
Southwestern Corn Borer Diatraea grandiosella (Dyar) corn
Tobacco Budworm Heliothis virescens (Fabricius) cotton


Resistance management strategy [136]

The 1998 Science Advisory Panel Subpanel agreed with EPA that an appropriate resistance management strategy is necessary to mitigate the development of insect resistance to Bt proteins expressed in transgenic crop plants.

The Subpanel recognized that resistance management programs should be based on the use of both a high dose and structured refuges designed to provide sufficient numbers of susceptible adult insects. The 1998 SAP also noted that insect resistance management strategies should be sustainable and to the extent possible, strongly consider grower acceptance and logistical feasibility.

High dose [136]

The Subpanel defined a high dose as 25 times the amount of Bt delta-endotoxin necessary to kill susceptible individuals. The Agency has adopted this definition of high dose. A Bt plant-pesticide could be considered to provide a high dose if verified by at least two of the following five approaches:

1) Serial dilution bioassay with artificial diet containing lyophilized tissues of Bt plants using tissues from non-Bt plants as controls;

2) Bioassays using plant lines with expression levels approximately 25-fold lower than the commercial cultivar determined by quantitative ELISA or some more reliable technique;

3) Survey large numbers of commercial plants in the field to make sure that the cultivar is at the LD99.9 or higher to assure that 95% of heterozygotes would be killed (see Andow and Hutchison, 1998);

4) Similar to #3 above, but would use controlled infestation with a laboratory strain of the pest that had an LD50 value similar to field strains; and 5) Determine if a later larval instar of the targeted pest could be found with an LD50 that was about 25-fold higher than that of the neonate larvae. If so, the stage could be tested on the Bt crop plants to determine if 95% or more of the later stage larvae were killed.

Effective IRM is still possible even if the transformed plant does not express the Bt protein at a high dose. If the Bt plant is non-high dose, the IRM plan could include increased refuge size, increased scouting and monitoring, and/or prohibition of sales of non-high dose products in certain areas.

Structured refuge [136]

A structured refuge is a non-Bt portion of a grower's field or set of fields that provides for the production of susceptible insects that may randomly mate with resistant insects that may emerge from Bt fields and dilute resistance. The size, placement, and management of the refuge is critical to the success of the high dose/structured refuge strategy to mitigate insect resistance to the Bt proteins produced in corn, cotton, and potatoes. The 1998 Subpanel defined structured refuges to "include all suitable non-Bt host plants for a targeted pest that are planted and managed by people.

These refuges could be planted to offer refuges at the same time when the Bt crops are available to the pests or at times when the Bt crops are not available." The Subpanel suggested that a production of 500 susceptible adults in the refuge that move into the transgenic fields for every adult in the transgenic crop area (assuming a resistance allele frequency of 5 x 10-2) would be a suitable goal. The placement and size of the structured refuge employed should be based on the current understanding of the pest biology data and the technology. The SAP also recognized that refuges should be based on regional pest control issues.

Insect resistant management imposed on registered Bt plant-pesticides [136]

To address the very real concern of insect resistance to Bt proteins, EPA has imposed IRM requirements on registered Bt plant-pesticides. Sound IRM will prolong the life of Bt pesticides and universal adherence to the plans is to the advantage of growers, producers, researchers, and the American public. EPA's strategy to address insect resistance is two-fold:

1) mitigate anysignificant potential for pest resistance development in the field by instituting IRM plans, and

2) better understand the mechanisms behind pest resistance. Beginning with the first Bt plant-pesticide registration, the Agency has taken steps to manage insect resistance to Bt with IRM plans being an important part of the regulatory decision. The Agency identified (later confirmed by the 1995 SAP) seven elements that should be addressed in a Bt plant-pesticide resistance management plan:

1) knowledge of pest biology and ecology,
2) appropriate dose expression strategy,
3) appropriate refuge,
4) resistance monitoring and aremedial action plan should resistance occur,
5) employment of integrated pest management (IPM),
6) communication and education strategies on use of the product, and
7) development of alternative modes of action.

Developing an IRM plan [136]

Key to developing an effective IRM plan is an understanding of the pest(s) biology, the dose ofthe protein expressed in the various plant tissues, and the size and placement of the refuge (a portion of the total acreage using non-Bt seed). It is believed that planting a refuge will delay the development of insect resistance by maintaining insect susceptibility. In addition to a structured refuge, IRM plans include additional field research, resistance monitoring for the development of resistance (and increased insect tolerance of the protein), grower education, a remedial action plan in case resistance is identified, annual reporting and communication. IRM plans will change as more scientific data become available. EPA, has in fact, changed IRM plans as new data has become available.

A summary of the Agency's risk assessment of insect resistance development and insect resistance management plans to mitigate resistance is provided below for Bt corn, Bt cotton, and Bt potato products. The detailed Agency risk assessments of insect resistance management are found in the following memoranda: A. Reynolds and R. Rose (OPP/BPPD) to M. Mendelsohn (OPP/BPPD), dated September 11, 2000; S. Matten (OPP/BPPD) to W. Nelson (OPP/BPPD), dated July 10, 2000; S. Matten (OPP/BPPD) to W. Nelson (OPP/BPPD), dated September 11, 2000; and S. Matten (OPP/BPPD) to W. Nelson and L. Hollis (OPP/BPPD), dated July 5, 2000.

Biologic control of the Indian meal moth and the European corn borer [137]

The wasp Trichogramma brassicae Bezdenko, Hymenoptera Trichogrammatidae, is a a parasitoid of Lepidopteran eggs. This activity of T. brassicae is used to control the the European corn borer and is now available to fight the Indian meal moths (Plodia interpunctella) .

Indian meal moths [137]

According to the Colorado State University Extension adult insects are small and have a broad, grayish band on their bronze-coloured wings. Immature Indian meal moths develope on dried food product, such as grain, dried fruits, nuts, crackers, powdered milk, bird seeds and dog food. Household infestations originate from purchase of infested foods, but come also from moths moving in from outdoors. Small, white worms and webbing indicate infested foods which must be discarded. To avoid losses the author suggests to place the food package in the freezer for several days, microwaving or warming up to 55° for three hours, to kill insect eggs and larvae.

The biologic control of moths [138]

Some biologic companies such as AMW, Germany, sell cards with attached eggs of moths which are parasited with Trichogramma brassicae or T. evanescens wasps as pupae. These cards may be placed in the infested storage compartment. After some days the pupae of Trichogramma brassicae hatch. Females search for eggs of the moth and lay eggs within them. The resulting larvae eat up the content of the infested egg of the moth.

Whiteflies [139]

According to the Agricultural Research Service (ARS) whiteflies are found throughout the tropics and subtropics, but can be troublesome in greenhouses and other growing environments as well. Both immature and adult stages ingest plant sap and cause damage directly, by feeding and transmitting plant viruses, or indirectly, by excreting a sticky substance called honeydew onto leaves and fruit.

Sooty mold fungi colonize the contaminated surfaces, further interfering with photosynthesis and ultimately resulting in reduced quality of fruit and fiber. In addition to ornamentals, whiteflies attack cassava, cotton, sweet potato, legumes and many other vegetables grown in mixed or annual cropping systems.

Control of whiteflies

The USDA maintains an online guide on whiteflies. The importance of crop hygiene, pre- and post-planting practices, insecticide recommendations and the need to control whiteflies early, before they spread to neighbouring fields is stressed.

Proper use of insecticides is important for whitefly management, particularly with respect to avoiding development of insecticide resistance in whiteflies. Insecticide misuse may result in silverleaf whitefly populations that cannot be controlled. The online guide stresses that the Q-biotype whitefly is already resistant to a number of products commonly used. Chemical overspray could easily lead to B-biotype resistance. Biotyping of whiteflies should be made to decide between the strategy to be applied. Samples of white flies may be sent to the given addresses which will see if it is the Q or the B biotype.

It is recommended that insecticides be rotated between chemical classes and should be applied a minimum of two times, at a five- to seven-day interval, to allow for egg hatch between applications and ensure that adults, nymphs and newly hatched individuals are all killed.

The USDA Agricultural Research Service (ARS) online guide can be accessed at:
http://www.mrec.ifas.ufl.edu/LSO/bemisia/bemisia.htm

Possible New Control for Whiteflies Discovered

The silverleaf whitefly, Bemisia argentifolii (previously known as B. tabaci biotype B), injures plants directly by feeding and indirectly by transmitting plant viruses. The plants become a yellow, mottled look and eventually die.

White flies have a natural resistance to pesticides. Repeated applications are needed resulting in hazard for environment, animal life or humans. Therefore biologic by natural enemies of the fly was studied by Cabanillas which proposed in 2001, the fungus Isaria propawskii. This fungus kills larval and adult stages of silverleaf whitefly. Isaria propawskii include establishment itself in a semiarid region where temperatures can reach 42°C and persists, even in the absence of insect hosts. It is also highly pathogen to the glassy-winged sharpshooter, Homalodisca vitripennis (previously known as H. coagulata) [140].

The female Eretmocerus mundus wasps may become another biocontrol of whiteflies. It produces marking pheromones, which are specialized lipids for marking whitefly nymphs they have chosen as egg hosts. This makes other wasps to choose another egg to lay their eggs. This avoids double-parasitizing turning the whitefly control very effective. The pheromones used by the wasps as markers were found to be C31 and C33 dimethylalkanes [141].

The Spotted Wing Drosophila fruit fly emerging fruit pest [142]

According to Amy Dreves, Vaughn Walton of the Oregon State University, the Spotted Wing Drosophila fruit fly Drosophila suzukii produced heavy damage in Oregon fruits in late 2009. Drosophila suzukii harms ripening fruit, while other Drosophila species do not harm the crop, because they infest overripe and fallen fruit. The insect is associated with raspberries. blueberries, peaches, raspberries, strawberries, plums and grapes.

Losses of one third of the cherry crop, 80 percent of peaches and 20 percent os raspberries are being reported in California. Pears and wine grapes are targeted by D. suzukii.

The Spotted Wing Drosophila is a close relative of the vinegar fly (Drosophila melanogaster), feeding on overripe bananas. spoiled and rotting fruit. The spotted wing Drosophila fly, in contrast, infests fresh fruit. The wild Himalayan blackberries could offer a refuge for overwintering populations of flies.

The researchers recommend to immediately remove and dispose infested fruit. And monitor for the presence of adult flies before they lay eggs.

The D.suzukii male flies have a pale black spot at the leading edge of the wing. Infestation starts with a small puncture wound on hanging fruit, which softens starting at the puncture scar, with subsequent decay, and mall pale maggots in intact fruit on the plant. [143]

Biologic control of the corn stem borer (Chilo partellus) [138] [144] [145]

This biologic control was used to reduce the infestation of corn fields with the corn stem borer. Trichogramma spp are sensitive to insecticides such as pyrethroids.

The correct timing is necessary, fresh infected eggs are therefore provided in an interval of two to three weeks. The chemical corporation BASF made researches with Trichogramma spp to control the corn stem borer, but abandoned the project in face of an enormous personal investment. The company turned therefore to support the genetic modified Bt-Corn which produces a protein which is toxic to the larvae of the corn stem borer.

A renaissance of the biologic method using cards with moth eggs infested with Trichogramma brassicae to protect extensive fields of corn is triggered by the concerns related to GM safety. Some companies such as Sautter & Stepper. Are specialised of a variety of biologic agents to control pests without chemicals.

With global tranportation of all kinds of goods, eggs, larvae and insects are being introduced in regions where these pests were unknown before. One pest is the box-tree pyralid (Glyphodes perspectalis), which migrated from East Asia to Europe causing damages in market garden. Its natural enemy is being surged for.


Citrus canker:USDA APHIS study not supported by scientifically sound evidence. [146]

The USDA APHIS evaluation of asymptomatic citrus fruit, (Citrus spp.) as a pathway for the introduction of citrus canker disease (Xanthomonas axonopodis pv. Citri) concludes that it is highly unlikely that citrus canker could be introduced on asymptomatic, commercially produced citrus fruit that has been treated with disinfectant dips and subject to other mitigations. Even if infected fruit were to enter a canker-free area with susceptible hosts, the establishment of citrus canker via this pathway appears to be unlikely.

The new Plant Health (PLH) Panel of the European Food Safety Authority (EFSA) evaluated a recent study on citrus canker disease published by the US Agriculture Department's Animal and Plant Health Inspection Services (APHIS) with special attention to its conclusion that citrus canker is not likely to spread by means of citrus fruit that show no signs of the disease. The PLH Panel concluded that key arguments in the study, and its conclusions, were not supported by scientifically sound evidence. [147]

Citrus canker is an economically significant plant disease caused by the bacterium Xanthomonas axonopodis pv. citri (Xac) affecting most of the citrus growing areas in the world, including Florida. Once established, various control methods including spraying of copper compounds must be combined to reduce the damage by Xac. [148]

Rigorous phytosanitary measures have insured that some areas, including Europe, are still free of the disease. These include the use of systems approaches. The current systems approach for the trade of citrus fruit requires that fruit are coming from disease-free area surrounded by a non-export buffer zone. The APHIS document proposes to modify the systems approach so that asymptomatic fruit coming from infected/contaminated areas are eligible for trade. [148]

The APHIS proposal to allow fruit from contaminated groves to be traded is a major deviation from existing phytosanitary measures. The APHIS document analyses the five events that must occur for successful introduction and proposes a new systems approach to prevent entry and establishment. However, no new or additional studies are presented and the analysis of the evidence provided in the document does not justify a change in the regulations. None of the preventative measures in the systems approach proposed by APHIS are shown to give effective control of Xac. Therefore, it can be concluded that, where an initial inoculum load exists, the transmission of Xac in the scheme proposed by APHIS is more likely than with the current systems approach. [148]

Citrus greening also known as huanglongbing [149]

Citrus greening, also known as huanglongbing (meaning "Yellow Dragon" for the yellow sectors of infected trees) was found on citrus trees in Asia, Africa, the Indian subcontinent and the Arabian Peninsula, Brazil and South Florida.

The spread of this disease must be carefully monitored to avoid further spread. Affected trees must be removed. It is caused by bacteria, such as 'Candidatus Liberibacter americanus' and 'Candidatus Liberibacter asiaticus'. The bacteria invade the phloem system of plants which yellow, decline, and die within a few years. An insect, the citrus psyllid spreads the bacteria.

The symptoms of citrus greening are blotchy mottle and leaf yellowing that spreads throughout the tree with lopsided fruit that fail to colour properly, which is similar to signs of nutritional deficiencies. First symptoms of the disease appear only after three to eight months following infection.

Lopes and colleagues 2009 studed the influence of temperature on the spread of the liberacter bacteria in sweet orange trees. The liberibacter titers in the trees were determined using quantitative, real time-PCR. The authors found that the multiplication of 'Ca. L. asiaticus' is not affected at 35°, while a temperature of 32° is detrimental to 'Ca. L. americanus'. Thus, 'Ca. L. americanus' is less heat tolerant than 'Ca. L. asiaticus'.

Cassava

As tapioca starch finds growing applications in global food industry the producing countries are highlighted: Nigeria is the largest producer of cassava, followed by Brazil, Thailand Indonesia and Congo. Floods, droughts and cassava mosaic virus threaten African tapioca yields, and low prices for cassava made Thailand farmers change from cassava to maize and sugar cane because of low prices of cassava. To counter this,Thai government plans to launch a futures market to stabilize the price. Bacteria harm cassava such as Phytomonas manihotis in Brazil, Bacterium cassava in Africa and Bacterium solanacearum in Indonesia. Insects like locusts, beetles and ants, rats, goats and wild pigs may devastate plantations.


Cassava geminiviruses may become a threat to the energy crop plant Jatropha curcas [150]

Ramkat et al. 2011 analysed the geminivirus contamination of Jatropha from Kenya and Ethiopia and cassava from Kenia, both belonging to family Euphorbiaceae. Jatropha samples were negative for the RNA viruses Cassava brown streak virus (CBSV), Cassava common mosaic virus and Cucumber mosaic virus, but a Defective DNA A of ACMV was found. Two Begomoviruses were found in Jatropa samples.

The authors also found CBSV in cassava samples, some of them were co-infected with cassava mosaic geminivirus. An improved methodology to predict evolutionary aspects of Begomoviruses in Jatropha are presented. And provide a reliable diagnostic tool for geminivirus in jatropha and cassava.

The authors stress that cassava geminiviruses infection of Jatropha might be spread wider than assumed. They warn that this virus may threaten plantations for biofuel production. To reduce the risk of the virus jumping from cassava to jatropa both fields should not be planted in near vincinity.

High mutation frequency of cassava geminiviruses [151]

Fondong and Chen 2011 write that seven species of cassava geminivirusesare are known. They are the most damaging vector-borne plant pathogens in Africa. The authors assessed the genetic variation in East African cassava mosaic cassava Cameroon virus (EACMCV) from naturally infected cassava and from experimentally infected Nicotiana benthamiana. Results showed that the populations of EACMCV in cassava and in Nicotiana benthamiana were genetically heterogeneous, showing that cassava geminiviruses exhibit a high mutation frequency.

Transmission of cassava geminiviruses [152]

Cassava geminiviruses are transmitted in a persistent manner by the whitefly Bemisia tabaci, by vegetative propagation using cuttings from infected plants and occasionally by mechanical means. The severity of cassava mosaic disease is impacted by environmental factors such as light intensity, wind, rainfall, plant density and temperature. Given that the viruses are transmitted by whitefly, the spread of the virus is going to depend largely on the vector.

Verticillium wilt diseases and their prevention

Verticillium wilt

The Verticillium dahliae fungus infects roots of vulnerable plants, moving into leaves and causing them to discolour. The diseased plant eventually wilts and die. The fungus can also infect and kill hundreds of other kinds of plants, including strawberries and tomatoes. Verticillium wilt in olive plants may cause significant yield losses. Jiménez-Díaz et al. 2012 described the disease aetiology, epidemiology, and disease control strategies and measures. [153]

Verticillium Wilt is a wilt disease caused by the funguses Verticillium dahliae and Verticillium albo-atrum. These funguses may harm cotton, tomatoes, potatoes, eggplants, peppers, olive trees and other plants. Chemical control is not effective. Crop rotation, use of resistant varieties and deep plowing are strategies to reduce the spread of the disease.

Prevention of Verticillium dahliae and V. albo-atrum diseases in trees and shrubs [154]

According to Arbofux, a database of diseases of trees and shrubs, the soil should be controlled for micromicroslerotia of Verticillium spp. Sufficient humidity and fertilisation schould be optimised. Lowering the pH level of the soil may reduce risk of infection. Mycelium are rendered harmless by composting. Biofumigation using special white mustard and oil radish reduce significantly the number of microslerotia in soil. Shredded material of diseased plants should not be left at the site. Critical crops, such as potatoes, should not be planted in fields for future plantation of trees and shrubs.

Detection of Verticillium dahliae in spinach seed [155]

Duressa et al 2012 point out that spinach seed produced in the U.S. and Europe are commonly infected with spores of Verticillium dahliae this fungus is soilborne, and contaminated seeds increase the density of spores in soil and induce the spread of Verticillium wilt epidemics on lettuce and other crops. The authors presented a quantification of Verticillium dahliae spores in spinach seed which may identify highly infected lots enabling a decision on of its use. The quantitative real-time PCR (qPCR) assay is based on Verticillium dahliae-specific primer pair (VertBt-F and VertBt-R). A quantification cycle value of $\ge$ 31 corresponded with a percentage seed infection of ± 1.3%.

Soil-Plating Method for Isolation of Fungi from Soil and Determination of inoculum density [156]

Soil plating metode is performed distributing 0.005–0.015 gram of soil throughout a thin layer of nutrient medium of 8-10 ml Czapek–Dox with 0.5 per cent yeast extract agar, acidified with phosphoric acid to pH 4.0 in a Petri dish. Shaking and rotating the dish may achieve proper dispersal of the particles, reports Warcup 1950.

Biocontrol of Verticillium wilt of potatoes [157]

Biocontrol of Verticillium wilt, caused by Verticillium dahliae in potatoes was studied by El Hadrami, Adam and Daayf 2011 The authors coated potato seeds at planting with extracts from Canada milk vetch and four bacterial strains antagonists to Verticillium. The authors report that all strategies were effective, and extracts from Canada milk vetch provided the best results.

Trichoderma spp. treatment of tomato plants as antagonists to Verticillium dahliae [158]

Jabnoun-Khiareddine et al. 2009 tested the activity of Trichoderma harzianum, Trichoderma viride and Trichoderma virens against Verticillium dahliae. The authors report that germination of Verticillium microsclerotia was completely suppressed after exposure to liquid cultures of the Trichoderma spp bacteria. Tomato plants treated with Trichoderma spp. spore suspensions experienced reduced severity of Verticillium wilt, inoculated with Verticillium dahliae, compared to control plants not treated with the antagonists.

PCR method to determine low density of Verticillium dahliae which may harm strawberry plantations [159]

Low soil inoculum densities of Verticillium dahliae can cause significant crop loss of strawberry. Determination of inoculum density by soil plating takes two month and delays planting decisions. Bilodeau describes a fast PCR method to estimate pathogen populations in the soil.

A multiplexed TaqMan real-time polymerase chain reaction (PCR) assay based on the ribosomal DNA (rDNA) intergenic spacer (IGS) was developed for Verticillium dahliae. Replicating four DNA extractions for each field sample obtains reliable results. An assay for Verticillium tricorpus on soil plates was also developed.

Quantitative PCR method for Verticillium dahliae to detect wilt-resistant lines of potatoes [160]

Potato early dying, also known as Verticillium wilt is caused by Verticillium dahliae. Only few cultivars are wilt- resistant. Atallah et al. 2007 developed a quantitative Q-PCR method to detect and quantify Verticillium dahliae based on a primer pair VertBt-F/VertBt-R of the beta-tubulin gene, achieving better results as compared to methods using primers PotAct-F/PotAct-R of the actin gene, designed for potato.

The authors write that the Q-PCR method is more sensitive and less variable than the time-consuming plating assays to control Verticillium dahliae-resistance of breeding lines.

Iceberg lettuce breeding for high resistance to fungus and microbes [161] [162]

Ryan J. Hayes, Krishna Subbarao and colleagues studied the disease verticillium wilt of iceberg lettuce. The lettuce collapses before firm nicely rounded heads are formed. The agent of the disease is the root-rotting fungus Verticillium dahliae.

The researchers selected seeds of three new lettuces varieties which are now available to plant breeders. The new varieties are meant for crossing with consumer-ready lettuces to boost the commercially grown lettuce's resistance to Verticillium wilt.

Verticillium dahliae count in soil

Verticillium dahliae can attack tomato, eggplant, pepper, potato, chrysanthemum, asters, fruit trees, strawberries, raspberries, roses, alfalfa, maple, elm and others. Damage to most fruit and vegetable crops may occurr if the Verticillium dahliae count in soil is high. This count is made when solanaceous crops such as potatoes, tomatoes, eggplant or peppers are to be grown. [163]

Lupinus polyphyllus Lindl. is a perennial ornamental belonging to the Leguminosae family. It is grown in gardens on flower beds and borders. Garibaldi and colleagues found the fungus Verticillium dahliae to infect up to 30% of this leguminous plants in Northern Italy. [164]

Corky root

Corky root is a disease caused by the bacterium Sphingomonas suberifaciens which causes lettuce roots to develop ugly, yellow-to-brown lesions that harden to a corklike texture. Corky-root-infected plants may produce stunted heads 30 to 70 percent smaller than normal.

Lettuce mosaic

The lettuce mosaic, is caused by a virus of the same name. It results in stunted growth as well as unattractive mottling of leaves. Green peach aphids can spread the virus from plant to plant.
Mou and Carolee T.Bull working at ARS are searching for corky-root-resistance genes that are different from the one already working inside the new parent lettuces to give lettuce additional corky-root-resistance genes.

Resistant varieties

Breeding lettuces with natural resistance remains the most environmentally friendly, economical and sustainable option for combating the fungus and microbes.

The authors conclude that because of the existence of resistance-breaking race 2 isolates, this resistance may not be durable. Alternatively, targeted releases of race-1-resistant cultivars to fields with only race 1 pathogen genotypes may extend the life of these cultivars.

Biotrophic Phytopathogens

Biotrophic phytopathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. They are limited to their adapted hosts, manipulating the host by secreting effector proteins, cell wall-degrading enzymes, toxins, phytohormones and exopolysaccharides. which damages the host plant. Effectors are proteins that are secreted from a pathogen, which suppress the immune system of the host organism. Hemibiotrophic organism parasites initially living tissues, it kills the host, later on, and continues its life cycle on dead tissues.

The fungi kingdom provides relevant plant diseases such as rust, powdery mildew, rice blast and cereal head blight which are aheavy burdon for commercial crops.

Kleemann et al 2012 identified effectors which mediate the opposing processes during the hemibiotrophic phases of Colletotrichum higginsianum infecting Arabidopsis. Most effector genes are host-induced and expressed in consecutive waves associated with pathogenic transitions, Effectors are focally secreted from appressorial penetration pores before host invasion demonstrating a high functional complexity for this fungal organ. Antagonistic effectors either induce or suppress plant cell death. [165]

Baltrus et al 2012 compared the genome, the genetic manipulation and the underlying mechanisms of Pseudomonas syringae and related strains isolated from different legume hosts. The type III secretion-independent virulence factors were found in the Pseudomonas strains. However, two genes encoding type III effectors (hopC1 and hopM1) were present, but the gene avrB2 was absent. This may explain the host range differences between pathovars glycinea and phaseolicola, and demonstrates the complex genetic host range evolution in plant pathogens, write the authors. [166]

According to Hückelhoven and Panstruga 2011, powdery mildew fungi is a typical obligate biotrophic parasites, which needs the interaction with living host cells. These phytopathogens induce re-organization of host cell architecture and physiology to be adapted to their own demands. Secretory processes are the key events at the plant-powdery mildew interactions. [167]

Effectors of powdery mildew [168]

Powdery mildews are phytopathogens whose growth and reproduction are entirely dependent on living plant cells. Spanu et al 2010 present the genome analysis of barley powdery mildew, Blumeria graminis f.sp. hordei (Blumeria), together with the analysis of two powdery mildews pathogenic on dicotyledonous plants. The authors note massive retrotransposon proliferation, genome-size expansion, and gene losses. The lost genes encode enzymes of primary and secondary metabolism unique of a biotrophic life-style. Less than 10 of effector of pathogenesis are found in all three Blumeria mildews. Over 200 other effectors are not commonly shared. The authors stress that they are species-specific adaptations.

Fungal plant parasites possess very plastic and dynamic genomes, which typically encode several hundred effector proteins secreted by lineage-specific genes on mobile and partly dispensable chromosomes. Such chromosomes determine the pathogenicity and the host range. They are transferred intraspecifically and possibly interspecifically and provide a lifestyle-specific adaptations of the genome optimising the pathogenicity of the fungus. [169]

Antifungal peptide Metchnikowin in trangenic barley responding to powdery mildew infection [170]

Antimicrobial peptides may increase disease resistance in transgenic crop plants. Rahnamaeian and Panstruga 2012 studied the impact of antimicrobial peptides of the Metchnikowin (Mtk) expression in transgenic barley modulating the immune responses of Mtk barley responding to biotrophic Blumeria graminis f. sp. hordei (Bgh). The activation of SAR pathway and the ISR pathway are increased. However, expression of Bax inhibitor-1 (BI-1) in transgenic and wild type plants were identical. This is caused by the neutrality in resistance/susceptibility of transgenic plants to Bgh, suggest the authors.

Clavibacter michiganensis subsp. Michiganensis causes tomato bacterial canker [171]

Clavibacter michiganensis subsp. michiganensis, causes tomato bacterial canker. It is transmitted by traded seeds, plant debris and on volunteer plants or alternative hosts that can act as local sources of inoculum. It is the disease of main economic importance in tomatoes. The pathogen colonises mainly the xylem vessels of the host.

The bacterium enters plant tissue through stomata and other natural openings, as well as wounds and roots. The bacterium survives for a long time in plant debris, soil and on equipment and glasshouse structures and more than 8 months in seeds. Isolation of the organism can be attempted on nutrient glucose agar or yeast peptone glucose agar. C. michiganensis subsp. michiganensis is described as slow-growing, smooth, shining, round, yellow colonies with entire margins. White, pink, red and orange mutants, however, do occur. C. michiganensis subsp. michiganensis is an aerobic, non-motile, Gram-positive, non-sporing, curved rod. Semi-selective media for isolation of the pathogen from seed extracts are not sensitive enough because of the presence of a saprophytic flora. [172]

Hvozdiak et al 2009 describe a mass tomato disease in farms of Ukraine caused by the Clavibacter michiganensis subsp. Michiganensis. [173]

According to Eichenlaub and Gartemann 2011 essential factors for disease induction are plasmid encoded and loss of the virulence plasmids converts these biotrophic pathogens into endophytes. Several serine proteases seem to be involved in colonization. A type 3 secretion system (T3SS) translocating effectors into the plant cells is absent in these gram-positive pathogens. The authors use in their reseache the modern "omics" technologies for RNA and proteins. [174]


Tomato wilt and canker of tomato [175]

The tomato wilt and canker of tomato is caused by the bacterium Clavibacter michiganensis subsp. Michiganensis . This bacterium is a vascular pathogen which depends on plasmid-borne virulence factors and serine proteases located on the chromosomal chp/tomA pathogenicity island (PAI).

Chalupowicz 2011 examined the colonization patterns and movement of the bacterium in inoculated plants. The wild-type strain Clavibacter michiganensis subsp. michiganensis NCPPB382 (Cmm382) infected of the whole tomato plant, reaching to regions in 15 days, forming biofilm-like bacterial agregates in the xylem walls.of the tomato plant.

The type Cmm100, which lacking the plasmids pCM1 and pCM2, and the type Cmm27 which lacks the chp/tomA PAI, did not move beyond the inoculation area. The authors suggest that the virulence factors are located on the chp/tomA PAI or the plasmids, being essential for the widespread invasion of the tomato plant.

Phytosanitary measures [172]

The European and Mediterranean Plant Protection Organization (EPPO) is an intergovernmental organisation responsible for European cooperation in plant protection in the European and Mediterranean region. Under the International Plant Protection Convention (IPPC), EPPO is the Regional Plant Protection Organization (RPPO) for Europe and is based in Paris.

EPPO has listed C. michiganensis subsp. michiganensis as an A2 quarantine pest. EPPO recommends that seeds be extracted by the hydrochloric acid method, or that the seed crop should have been inspected during the growing season.

Clavibacter michiganensis subsp. Nebraskensis, pathogen of corn [176]

Clavibacter michiganensis subsp. nebraskensis (CMN) is a gram-positive bacterium. It is the cause of Goss's bacterial wilt and leaf blight or "leaf freckles" in corn. Agarkova et al 20011, using amplified fragment length polymorphism (AFLP) analysis and repetitive DNA sequence-based BOX-PCR identified a major group A (n = 118 strains) and a minor group B (n = 13 strains).

Olive plants

Mercado-Blanco and colleagues developed a nested-polymerase chain reaction (PCR) procedure based on the simultaneous amplification of both an ND- and a new D-specific marker by means of duplex, nested PCR. This procedure helps to certify pathogen-free planting material and accurate detection of defoliating (D) and nondefoliating (ND) Verticillium dahliae pathotypes infecting olive plant. [177]

Jacobs and colleagues (1994) reported interspecific variation in susceptibility to Verticillium wilt caused by Verticillium albo-atrum Reinke and Berthier and Verticillium dahliae in redbud, and that Cercis yunnanensis is susceptible to the disease. [178]

Sanogo and Clary (2003) report that Verticillium dahliae recovered from the weeds Physalis wrightii (Wright groundcherry), Anoda cristata (spurred anoda), and Proboscidea louisianica (devil's-claw),is pathogenic to Chile pepper.
Control of Wright groundcherry, spurred anoda, and devil's-claw may be important in the management of Verticillium dahliae in chile pepper. [179]

Al-Rawahi and Hancock (1998) found the fungus Pythium oligandrum to be a parasite of Verticillium dahliae in dual culture, impeding the latter's ability to grow and form microsclerotia. Pepper grown in soil infested with V. dahliae, shoot and fruit weights were significantly higher in the presence of P. oligandrum than in its absence. When soil was infested only with P. oligandrum, fresh weights of shoots and fruits were 40 to 50% higher than when plants were grown in its absence. The authors find that improved plant health associated with soil treatment with P. oligandrum could be the result of complex interactions between pathogen, host, and mycoparasite. [180]

Spink and Rowe (1989) evaluated Talaromyces flavus as a potential biological control agent of Verticillium dahliae on potato, but found no significant effect on disease development, tuber yield, or percent recovery of V. dahliae from rhizosphere or nonrhizosphere soil at harvest. [181]

Page and colleagues (1991) studied the loss in irrigated alfalfa (Medicago sativa) attributable to Verticillium wilt (caused by Verticillium albo-atrum) was determined by comparing yields of resistant and susceptible cultivars grown in the presence of Verticillium wilt and developed equations for making economically sound decisions for managing alfalfa under the consederation of losses due to Verticillium albo-atrium [182]

Insect pest control using nematodes [183]

Nematodes are roundworms. Some can displace chemical pesticides in the fight of insect, slug, fleas, ticks and lice pests. Some nematodes are efficient against the root-feeding citrus weevil, black vine weevils, beetles, leas, and cutworm. The nematodes releasing a bacterium that kills the pest. However, others are parasitic and cause disease in plants, animals and humans

The skin of nematode secretes a flexible outer layer called cuticle. Which is shed four times during growth. Nematodes have no circulatory or respiratory system and are therefore dependent on favourable environmental conditions.

According to the USDA Agricultural Research Service (ARS) the peachtree borer (Synanthedon exitiosa attacking peach is being cotrolled by handgun application of chlorpyrifos to trunks. However, it does not work with the aggressive lesser peachtree borer (Synanthedon pictipes). Seeking environmentally friendly alternatives to organophosphates the ARS suggests to implement biological control of both peachtree borer and lesser peachtree borer in orchards by using entomopathogenic nematodes such as the nematode Steinernema carpocapsae.

Entomopathogenic nematodes [184]

Entomopathogenic nematodes are soil-inhabiting, lethal insect parasitoids which may be used as biological control agents. Liu, Pinar and Berry 2000 stress the importance of phylogenetic reconstruction to understand the interactions among entomopathogenic nematodes, symbiotic bacteria, and their insect hosts to select appropriate nematode species for a particular control programs.

Stealth worms [185]

According to Patricia Stock and colleagues 2005, worms of the family Heterorhabditidae are associated with Photorhabdus bacteria which live in its intestine. These bacteria are pathogen to certain insect species. Other nematodes in the family Steinernematidae live in symbiosis with Xenorhabdus bacteria. The nematodes enter a host, grub or larvae where it vomits the bacteria, which kills the host within 24 to 48 hours, building a perfect environment for the nematode to grow and multiply. Only juvenile nematodes survive dry conditions in soils for long periods of time.

Entomopathogenic nematodes are found in deserts, rainforests, grasslands and other ecological systems. Stock and co-authors search for these nematodes in all these habitats, also in Jordan. The aim of the researchers is to develop environmentally safe alternative for controlling insect pests in agricultural and forestry systems. Identification uses traditional morphology (structure and function) techniques and molecular screening. The right nematode is suspended in a gelatinous matrix, or dried in powder, then mixed in water and sprayed, broadcast or irrigated onto crops.

Transgenetic strategies to control insect pests

Insect toxins of Photorhabdus luminescens as alternative to Bt toxins [186]

Richard ffrench-Constant and colleagues 2007 describe the bacterium Photorhabdus luminescens which lives in symbiosis with nematodes, similar to Xenorhabdus bacteria of the entomopathogenic nematodes describe by Patricia Stock. Toxins of these bacteria kill a wide range of insects comparable to Bacillus thuringiensis (Bt) whose gene which express the Bt toxin were introduced in crop plants like transgenic cotton and corn. Insects are becoming resistant to Bt toxins. The toxin complexes of Photorhabdus bacteria are proposed by the authors as an alternative to Bt. The toxins can be used as a spray, and the toxin-producing genes may be introduced in the crop plants, which is considered by the auhors, to be the most effective strategy.

Plant-parasitic nematodes

The genome of important plant-parasitic nematodes sequenced [187]

Pierre Abad and colleagues 2008 report the sequencing of the genome of the nematode Meloidogyne incognita, known as the southern root-knot nematode which seriously affects crops of tomato, cotton and coffee. The knowledge of its genome may help to fight this worldwide plant-parasitic nematode. The authors suggest that ancient allelic regions in Meloidogyne incognita are evolving toward effective haploidy, permitting new mechanisms of adaptation. Multiple horizontal gene transfers from bacterial sources may be the origine of the high number and diversity of plant cell wall-degrading enzymes in Meloidogyne incognita.

Sequencing revealed that Meloidogyne hapla, also known as the northern root-knot nematode, similar to Meloidogyne incognita, is a diploid that reproduces by facultative, meiotic parthenogenesis. Both root-knot nematode genomes have smaller genome compared with the free-living nematode Caenorhabditis elegans, and both encode large suites of enzymes targeting the host plant. Oppermann and colleagues 2009 suggest that the small genome of the root-knot nematode compared with soil nematodes result from the fact that the nematode living inside of the host plant's roots is protected from the environment. [188]

Mi-1, N and Tabasco genes of tomato and pepper genotypes fail to protect against Meloidogyne mayaguensis [189]

Meloidogyne mayaguensis is a damaging root-knot nematode able to reproduce on root-knot nematode-resistant tomato and other economically important crops such as bell pepper and sweet pepper.

Brito and colleagues 2007 report that Meloidogyne mayaguensis infects the Mi-1-carrying tomato genotypes BHN 543, BHN 585, BHN 586 and Sanibel. Meloidogyne incognita harmed these tomatoes only under special conditions. Meloidogyne mayaguensis infects the roots of root-knot nematode-resistant bell pepper Charleston Belle carrying the N gene and on three root-knot nematode-resistant sweet pepper lines carrying the Tabasco gene. In contrast, The authors stress that Meloidogyne mayaguensis may overcome the resistance expressed by Mi-1, N and Tabasco genes of tomato and pepper genotypes of resistant cultivars of tomato and pepper, limiting their use to control the nematode infection.

Other biological strategies to control pests

New peanut hybrid Variety is resistant To Nematodes an virus [190]

Peanut varieties exhibit resistance to either the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1 or the tomato spotted wilt virus (TSWV). The geneticist geneticist C. Corley Holbrook in the Agricultural Research Service (ARS) 2008 hybridized both varieties of peanut plants. The resulting variety called Tifguard, has resistance to both diseases and presents higher yields compared with standard varieties.

Alternatives to methyl bromide to control nematodes [191]

Thies and colleagues 2008 tested the resistance to nematode of two types of bell peppers, Charleston Belle and Carolina Wonder. These cultivars are the only nematode-resistant varieties available.

The authors say that nematode-resistant varieties such as Charleston Belle and Carolina Wonder are viable alternatives to methyl bromide for managing southern root-knot nematode in bell pepper in sub-tropical environments. Nematode-resistant hybrid bell peppers from Charleston Belle and Carolina Wonder are being developed. Nematode-resistant bell pepper cultivars may displace fumigation of soil with methyl bromide before planting, say the authors. Methyl bromide is a gas widely used as plant pesticide. It depletes the ozone layer of the atmosphere, being phased out in USA.

Control of Mediterranean fruit fly with the parasitoid Muscidifurax raptor [192]

Jean Pierre Kapongo and colleagues 2007 assessed the possibility to use the parasitoid, Muscidifurax raptor to control of the Mediterranean fruit fly Ceratitis capitata in vineyards, where biologic strategies are used to displace chemical pesticides. Muscidifurax raptor prooved to be efficient to control house fly Musca domestica pupae in poultry houses. The authors report that there was no reduction of the number of eggs of the parasitoid laid in vineyard compared with the release in poultry houses. The authors suggest the use of Muscidifurax raptor as biocontrol agent for the control of the Mediterranean fruit fly in vineyards, and control flies in poultry houses, dairies and horse stables.

The adult parasitoid Muscidifurax raptor stings the fly pupa, killing the pupa and then lays an egg in the pupal case. When the egg hatches, the larva feeds on the dead fly pupa. In 19-21 days, the M. raptor adult emerges from the fly pupal case and begins its search for fly pupae on which to feed and deposit eggs. [193]


Red palm weevil may pose a risk to date production [194]

The red palm weevil (Rhynchophorus ferrugineus) became a risk to date palms pest lays its eggs on the bark of the date, coconut, oil, sago and other ornamental palms . Invasion spreaded from the Near East, the north of Africa and the European Meditarranean region. The weevil causes a total loss of the palms and rotting of the trunk which lead to the death of the tree. Adult females lay eggs in the crown of palm trees, larvae then penetrate the crown and later to most parts of the upper trunk, making tunnels of up to 1 m long. Pupation takes place in a cocoon under the bark.

Date palm is an important crop in north African countries and ornamental palms are widely planted as amenity trees in the whole Mediterranean area.

Phytosanitary measures taken in Israel according to Hamburger, Bitton and Nakache 2003: [195]
  1. R. ferrugineus was declared a quarantine pest, and pheromone traps were installed.
  2. Mass trapping of 10-12 traps/ha was organized and to 1 trap/3 ha in non-infested areas).
  3. Chemical treatments of infested trees.
  4. Destruction of heavily infested trees.
  5. Preventive measures to avoid infestations (drip irrigation to maintain trunk dry, removal of offshoots, preventive sprays on trunks).
The authors concluded that mass pheromone trapping might have played a significant role in the suppression of red palm weevil populations in date plantations.

Dogs to find the weevil [196]

The tree being damaged by the weevil exudes a foul odour. Humans can eventually detect this smell but not soon enough to save the tree, which can be done, if caught in time, with Golden Retriever dogs are used in a joint Israeli-Arab project by the Shimon Peres Center for Peace, researchers. These dogs detect the presence of the grubs in the early stages of infestation when an injection of insecticide still may save the palm.

Leaf cutting ants

[197] Leaf-cutting ants such as Atta sexydens and Acromyrmex octospinosus live in Argentina, the south of Brazil including the state of São Paulo. Acromymex spp was imported in the south of the U.S.A. From Argentina by food transportation. The ants cause heavy damage to agriculture and defoliate a tree in one night. It is speculated that if Atta sexdens would spread into tropical Africa, results would be devastating. As the local plants have not developed defensive compounds against leaf cutters and Africa does not have parasites evolved to infect them, the results for both the ecosystem and agriculture would be devastating. [198]

The ants live in obligate symbiosis with fungi of the genus Leucoagaricus, which grows on leaf brought into the nest by the ants. The ants depend on the fungus material as their food. They do not eat the leaves. It is the fungus they grow from which they feed. Pathogenic fungus Escovopsis sp. can overcome the useful Leucoagaricus sp. fungus and the colony starves.

The authors found that ant-associated microorganisms such as Pseudonocardia, Dermacoccus, and Streptomyces control the invasive fungus Escovopsis. The strain Streptomyces sp. produces the antibiotic candicidin which is effective against Escovopsis but does not interfere in the growth of the ant food fungus.

Hygiene strategy of ants avoid changes of their fungal cultivar [199]

Leaf-cutting ants maintain an obligate symbiosis with their fungal garden. The ants and their cultivar have to cope with hundreds of endophytic fungal species which are brought in with the leave cuts.

Endophytes

Endophytes are a bacterium or fungus, that live within a plant for at least part of its life without causing apparent disease. Endophytes may benefit host plants by preventing pathogenic organisms from colonizing them. Fungal endophytes may outcompete the fungal cultivar of the nest.

Van Baels and colleagues 2009 found that ants control endophytes applying strategies like preferring to cut leaves from low endophyte densities, they reduce the amount of endophytic fungi in leaves before storing them in their nest and the original fungal cultivar inhibits the growth of foreign fungi that might out-grow the cultivar.

Fifty million years of evolution moulded the leaf-cutter ants [200]

Entomologists Ted Schultz and Seán Brady explain that agriculture is a specialized form of symbiosis which evolved in only four animal groups: humans, bark beetles, termites, and ants. Evolution produced the five distinct agricultural systems of the fungus-growing ants, resulting from a single ancestor living 50 million years ago.

In the past 25 million years, four different specialized agricultural systems have evolved, leading to the most recently evolved and best-known fungus-growing ant species-leaf-cutter ants. Leaf-cutter ants originated recently-less than 10 million years ago.

Ants depend on fungus but the fungus does not depend on the ants [201]

The fungal garden which serves as food for the ant colony is grown from a few strands of the garden of origin. The queen carries them in her mouth on her mating flight to start a new colony. Mikheyev, Mueller and Abbot 2006 describe evidence of recombination in attine fungal cultivars, contradicting widely held perceptions of obligate clonality.

Mikheyev and Mueller 2006 studied the coevolutionary process of the dependence of fungus-farming ants on fungus gardens for food. The researchers found that the ants were dependent on the fungus, but no dependence of the fungus on the ant was stringent. The fungus-growing ants were seen as a coevolutionary integration.

The fungi occasionally reproduce sexually by spores carried by wind. It exchanges genes with other ant-cultivated fungi. According to genetic analysis made by the authors the fungus of Cuba exchanged genes with mainland fungi populations of Central and South America brought in by winds. The fungus is still using its sexual reproduction and is not completely dependent on asexual, clonal reproduction through their ant farmers. This is an example that coevolution does not imply mutual dependence.

Coevolution

Biological coevolution is the change of a biological object triggered by the change of a related object. Coevolution can occur at multiple levels of biology: it can be as microscopic as correlated mutations between amino acids in a protein, or as macroscopic as covarying traits between different species in an environment. Each party in a coevolutionary relationship exerts selective pressures on the other, thereby affecting each others' evolution. Species-level coevolution includes the evolution of a host species and its parasites, and examples of mutualism evolving through time

A species may evolve in response to a number of other species, each of which is also evolving in response to a set of species. This situation has been referred to as "diffuse coevolution". And, certainly, for many organisms, the biotic (living) environment is the most prominent selective pressure, resulting in evolutionary change. [202]

Yeasts associated with leaf-cutting ants [203]

Carrero and colleagues 1997 isolated 137 yeasts associated with the leaf-cutting ant Atta sexdens rubropilosa Forel, 1908. Candida, Cryptococcus, Rhodotorula, Sporobolomyces, Tremella, Trichosporon, Pichia and black yeasts were isolated by the authors. The genus Candida was widely distributed, with C. homilentoma, C. colliculosa-like, C. famata and C. colliculosa being the most prevalent.

Leave-cutting ant control strategies, Chemical control [204]

Atta sexdens rubropilosa Forel, 1908 "Lemon fire ant"

Crush the head of a soldier ant between your fingers. A lemon-like odor characterises this ant.

Atta sexdens piriventris Santschi, 1919 "Southern lemon fire ant"

Same identification as foregoing.

Atta laevigata F. Smith, 1858 "Glas had fire ant "

The largest workers of the colony have a smooth and shining head, similar to glass.

Atta bisphaerica Forel, 1908 "Yellow fire ant"

Its colour is brown-yellow not shining.

Atta capiguara, 1944 "grass-cutting ant"

It prefers grass instead of leaves. It differs from the foregoing ants in not producing a lemon smell, it is not brilliant,Its head is not brown yellow

It is recommended to find vertical holes which lead directly to the centre of the colony to apply the liquid poison, powder or fumes. Baits should be left on the trail of the ants. Application of poison must follow the instructions of the producer.

Chemical used in form of gases and powder are applied directly to the nest. Baits are carried to the fungal garden by worker ants but are not accepted by all sort of ants. The strategy varies according to the ant which is to be controlled. It is difficult to eradicate leaf cutter ants with dust, liquid or granular insecticides because the centre of the nests, with the fungal garden is often missed. Bits are often not accepted. Baits with hydramethylnon are in use to control leaf cutting ants. [205]

Phorid flies [206]

Wuellner and colleagues 2002 suggest biocontrol of leave-cutting ants using phorid flies such as Pseudacteon tricuspis and Pseudacteon obtusus for the control of the red imported fire ant in geographical areas where polygyne colonies dominate, such as Texas. For Florida, where monogyne colonies dominate, Pseudacteon litoralis is being recommended by the authors.

Gyne

Gyne is the primary reproductive female caste of social insects (especially ants, wasps, and bees of order Hymenoptera). Gynes are those destined to become queens, whereas female workers are typically sterile and cannot become queens. A colony with multiple queens is said to be a polygyne form, where as with only one is a monogyne form. The fire ant Solenopsis invicta is known to have colonies in both polygyne and monogyne forms. [207]
Female phorid flies Pseudacteon obtusus were released in Texas in 2008-2009. The flies inject their eggs into the ants. The resulting larvae migrate to the ant's head where it feeds from the ant's brain and decapitates its host to hatch. [208] [209]

The combination of biocontrol using phorid flies in combination with chemical poisoning of ant colonies is being suggested. The chemical control is very effective, but does not avoid a new infestation from colonies which had been overseen.

Pheromone studies may lead to new biologic control of leave-cutting ants [210]

Insect hormones. More than 90% of insect hormones are neuropeptides. Researchers try to understand the function of insect neuropeptides, which are hormones which have important functions during insect developmental and as adults. With increase knowledge on this matter dependence on poisonous chemicals may be reduced.

Choi, Raina and Vander Meer 2009, studying the fire ant, Solenopsis invicta, found the pyrokinin/pheromone-biosynthesis-activating neuropeptide (PBAN), which is a family of peptides. This pentapeptide stimulates the production of pheromone in female moths, muscle contraction, induction of embryonic diapause, melanization, acceleration of puparium formation, and termination of pupal diapause.

The authors hope to increase knowledge about the regulation of pheromone production their release, and how neuropeptides they influence the development of ants. Researches in this field may create non-insecticide methods for fire ant control by interfering in the normal neuropeptide hormone function.

Gene controlling root-hair cells growth may increase plant yield in nutrient poor soils [211]

Plants interact with the environment releasing chemicals which solubilise nutrients such as iron and phosphate. Root-hair cells are responsible for such plant activities. Long-haired beans, barley and wheat grow better than those with short hairs.

Yi and colleagues 2010 found that Arabidopsis thaliana increase the size of their root hairs when growing in phosphate poor soils. This was due to the expression of the basic helix-loop-helix (bHLH) transcription factor called RSL4 gene which regulates the growth of these hairs following endogenous and environmental signals such as low phospahte availiability or auxin.

Their findings may lead to cultivars which can grow on soils poor in iron and phosphate, such as soils in Australia, the sub-Saharan Africa and China. It also could reduce the need of fertilisers, decreasing the amount of polluting phosphate that runs off into rivers and lakes.

Mathematical approach to test how hot chilli peppers are [212]

Capsaicinoids are the spicy compounds of chilli peppers. These compounds act on pain receptors in the mouth and throat, producing a burning sensation in the tissue and triggers increases in heart rate and perspiration, as well as the release of endorphins . They can be analysed using liquid chromatography. To reduce costs of such chemical analysis Kennet Bush and colleagues 2010 developed a multivariate regression analysis which is a mathematical approach comparing unknown pepper with spectral data of known plant types and predicts the hot taste

of the unknown pepper. Such test will be valuable for food quality monitoring.

The Scoville Organoleptic Test [213]

The Scoville scale is a measurement of the spicy heat of a chili pepper. Results are given in number of Scoville heat units (SHU). In Scoville's method, an alcohol extract of the capsaicin oil from a measured amount of dried pepper is added incrementally to a solution of sugar in water until the "heat" is just detectable by a panel of (usually five) tasters; the degree of dilution gives its measure on the Scoville scale. Thus a sweet pepper or a bell pepper, containing no capsaicin at all, has a Scoville rating of zero, meaning no heat detectable. The hottest chilis, such as habaneros and nagas, have a rating of 200,000 or more, indicating that their extract must be diluted over 200,000 times before the capsaicin presence is undetectable. The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity. Tasters taste only one sample per session.

Spice heat is usually measured by a method that uses high performance liquid chromatography (HPLC). The concentration of heat-producing chemicals measured by HPLC may be used in a mathematical formula which compares it with heat sensation. This method gives American Spice Trade Association (ASTA) pungency units. One part capsaicin per million corresponds to about 15 Scoville units, and ASTA pungency units can be multiplied by 15 and reported as Scoville units

Clinical properties of capsinoids of CH-19 sweet pepper are comparable to hot chilli pepper [214]

Luo, Peng and Li 2010 write that capsaicinoids of hot chilli peppers consist of capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin, and others. Capsaicinoids are looked at for pain relief, cancer prevention, weight loss, display benefits on cardiovascular and gastrointestinal system, and act as agonists of capsaicin receptor or transient receptor potential vanilloid subfamily member 1 (TRPV1).

TRPV1 is a nonselective cation channel that may be activated by a wide variety of exogenous and endogenous physical and chemical stimuli. The best-known activators of TRPV1 are heat greater than 43° and capsaicin, the pungent compound in hot chilli peppers. The activation of TRPV1 leads to painful, burning sensation. Its endogenous activators include: low pH (acidic conditions), the endocannabinoid anandamide, N-arachidonoyl-dopamine. TRPV1 receptors are found mainly in the nociceptive neurons of the peripheral nervous system, but they have also been described in many other tissues, including the central nervous system. TRPV1 is involved in the transmission and modulation of pain (nociception), as well as the integration of diverse painful stimuli. [215]

Capsinoids

Luo and colleagues stress that capsinoids from CH-19 sweet peppers present similar structure with capsaicinoids and consist of capsiate, dihydrocapsiate, and nordihydrocapsiate and others. They are less

pungent and less toxic than capsaicinoids and present the same cancer prevention and weight loss properties of capsicinoids.

Naga chilli, the hottest chilli in the world [216]

Naga chilli or Bhoot Jolokia (Capsicum chinense Jacq.) of the northeast region of India is the hottest chilli in the world. Meghvansi and colleagues in a review stresses the potential of capsaicinoids in various ethnopharmacological applications such as pain therapy, body temperature regulation, anti-obesity treatments, anticancer therapy and as antioxidant and antimicrobial agent, where scientific researchis needed to close the gap between traditional medicinal knowledge and modern medicine.

Liu and Nair 2010 found capsaicin (C) and dihydrocapsaicin (DHC) in Bhut Jolokia (Capsicum chinense Jacq.) to be 5.36% and was about 338 and 18 times greater than hot peppers Jalapeno (Capsicum annuum) and Scotch Bonnet (Capsicum chinense). The authors also determined lipid peroxidation and cyclooxygenase (COX-1 and -2) enzymes inhibitory concentrations. [217]

Analysis of capsaicin and dihydrocapsaicin [218]

Peña-Alvarez, Ramírez-Maya, Alvarado-Suárez describe the analysis of capsaicin and dihydrocapsaicin in peppers and pepper sauces by solid phase microextraction-gas chromatography-mass spectrometry.

Pungency of chilli pepper is a response to microbes [219]

Tewksbury and colleagues 2008 suggest that the pungency in chillies may be an adaptive response to a microbial pathogen. The authors report that geographic variation in the production of capsaicinoids of chilli pepper Capsicum chacoense was directly linked to the damage caused by a Fusarium fungus to the seeds of the chilli pepper. The authors concluded that capsaicinoids protect chilli seeds from the fungus and insects which feed on the seeds and facilitates the entry of Fusarium mould in the seeds, the primary cause of predispersal chilli seed mortality.

Size of apples vary according to cell division [220]

Malladi and Hirst 2010 found that endoreduplication was causing an anomaly in some Gala apple trees, causing apples to grow 38 percent heavier and 15 percent larger in diameter than regular Gala apples. This anomaly caused cells to grow without splitting. The Gand Gala had the same number of cells as the smaller Gala apples, however Grand Gala cells were larger. The authors write that due to endoreduplication the cells in Gand Gala duplicate their nucleus material but do not split the cell as it happens in Gala apples.

Higher gene MdCDKA1 at 8 DAFB expression and reduced MdCYCA2 expression regulates the mitotic cell cycle as well as endoreduplication during early fruit development in Grand Gala apples. There is a commercial interest to find out what genes are responsible for a weight gain of apples because bigger apples attain better price on the market.

Endoreduplication is replication of the nuclear genome without cell division resdulting in polyploidy. Endoreduplication is often found in plants. According to Barow 2006 endopolyploidy provides support of high synthetic demands in certain cells and complements small genomes. In seed plants endopolyploidy has an impact on growth and development and are an adaptation to drought stress. Endopolyploidy is found in some tissues where cell size is important for specific cell functions [221].

Cookson et al 2006 defined the DEL1 gene to be involved in endoreduplication of plant leave cells under drought stress. [222]

Locked chromophores help to understand the light sensor of plants [223]

Plant photoreceptors, called "phytochromes" contain bilin chromophore. Light triggers the conversion between the red light-absorbing form, Pr, and the far-red-light-absorbing form, Pfr of bilin. A chemical construct induced plant development in absence of light.

Lamparter et al. 2012, at the Karlsruhe Botanical Institute, Germany, explain that plants depend on sunlight which provides energy and also steers the development of seed till the formation of leaves and flowers. Orientation of the plant related to gravity and gene regulation are also affected by light. Plants were outwitted by feeding them15 E anti phycocyanobilin (15EaPCB), a locked phycocyanobilin derivative. The seeds started to grow in complete darkness as long initial energy reserves lasted.

The absorption spectra of the 15ZaPCB and 15EaPCB adducts were comparable with those of the Pr and Pfr form, respectively, but only 15EaPCB started plant cell activity in darkness, resulting in the formation of active Pfr-like phytochrome in the cell. The authors stress that locked chromophores may be useful for further researches on plant light sensor system.

Grafting [224]

Grafting is a method of attaching the root of one tree to the shoot of the desired fruit to clone it In most cases, one plant is selected for its roots, and this is called the stock or rootstock. The other plant is selected for its stems, leaves, flowers, or fruits and is called the scion. The scion contains the desired genes to be duplicated in future production by the stock/scion plant. In stem grafting, a common grafting method, a shoot of a selected, desired plant cultivar is grafted onto the stock of another type. In another common form called budding, a dormant side bud is grafted on the stem of another stock plant.

The vascular cambium tissues of the stock and scion plants must be placed in contact with each other. Both tissues must be kept alive until the graft has taken, usually a period of a few weeks. Successful grafting only requires that a vascular connection take place between the two tissues. A physical weak point often still occurs at the graft, because the structural tissue of the two distinct plants, such as wood, may not fuse.

McNellis and colleagues are trying to selectively pick traits to copy by using the root to turn on and off desirable genes in the shoot, taking the root of a small Crab Apple tree and grafting it to the shoot from a tasty Gala apple can produce a small tree with great fruit. Rootstocks can turn on genes already present in the scions. McNellis tries to determine the links between specific genes and the most desirable apple traits, especially disease resistance, such as fireblight disease. [225]

Grafting technique [226] [227]

Grafts must be made between genetically similar plants. Usually, species to species. During grafting the cambial regions of the scion and understock must line up so that the vascular systems can reattach.

Interstock

An interstock or interstem is placed between the scion and the understock. This is called double working. Tis is used with fruit tree grafts where the scion and understockare incompatible, but the interstock is compatible with both the scion and understock.

Fire blight [225]

Fire blight is a bacterial infection which attacks apples, pears, and some other members of the family Rosaceae, and kills from the inside out, leaving brown and brittle trees which look like being damaged by fire. It is caused by the bacterium Erwinia amylovora. McNellis explains that one kind of rootstock turned on twice as many stress tolerance genes in the scion. Choosing the right rootstock to protect generations of Gala apple trees from the ravages of fire blight.

Sprays of the antibiotics streptomycin or terramycin can prevent new infections. The use of such sprays has led to streptomycin-resistant bacteria in some areas, such as California and Washington. The only effective treatment for plants already infected is to prune off the affected branches and remove them from the area. Plants or trees should be inspected routinely for the appearance or new infections. [228]

Glyphosphate-resistant superweeds in Missouri plantations of soy an cotton and corn [229]

Soy and cotton crops in U.S, are threatened by weeds, such as common waterhemp population, glyphosate resistant giant ragweed and horseweed (Conyza canadensis (L.) Cronq.) resistant to multiple herbicide mechanisms of action including ALSinhibitors (MOA Group 2), PPO-inhibitors (MOA Group 14), and glyphosate (MOA Group 9 EPSP synthase inhibitor).

Representatives from the U.S. Environmental Protection Agency, the Department of Agriculture and the Weed Science Society of America (WSSA)are worried about the impact of rising weed resistance. Some groups have suggested that glyphosate-resistant weeds are "super weeds" which will spread and compromise native ecosystems. The evolution of weeds with multiple herbicide resistance has made producing crops economically an increasing challenge for producers.

The WSSA writes that the problem began in the 1990's when waterhemp populations evolved resistance to the triazines (MOA Group 5 Photosystem II-inhibitors) and ALS-inhibitng herbicides (Group 2), followed with resistance to the PPO-inhibiting herbicides (Group 14) by 2000, and glyphosate (Group 9) in 2005. Some weeds developed resistance to herbicides with four or five different mechanisms of action.

The university of Illinois and USDA weed scientists decided to follow up and determine the feasibility and efficacy of including fluridone as a management tool for Palmer amaranth in cotton production systems or ditches. The WSSA concluded that tillage, hand-weeding to manually reduce the amount of glyphosateresistant weed seed production as a long-term management strategy, demonstrate the dependence of growers on effective herbicides for weed management and other nonchemical means such as cultural practices and crop rotations will be needed to supplement herbicides in future weed management strategies to enhance the sustainability of the system.

According to Tom Wiltrout the Dow AgroSciences is introducing an herbicide and seed system called Enlist as an alternative to Roundup. [230]


The banana bunchy top virus

Banana bunchy top virus (BBTV) spread into 11 countries in the sub-Saharan Africa region reducing yields of bananas and plantains (Musa spp.) crops. Nucleotide sequences of DNA-S and DNA-R of BBTV isolates from these countries are genetically identical to the 'South Pacific' phylogroup which include Australia, Egypt, South Asia and South Pacific. [231]

Kumar et al 2011 deduce from these data that transferring vegetative propagules together with virus spread by the banana aphid vector, Pentalonia nigronervosa, are the reason of the rapid expansion of of the virus, and phytosanitary programs are suggested for the management of the virus and their vector.

Yu et al 2011 isolated, cloned and sequenced a banana bunchy top virus sample. It is a single stranded DNA virus (ssDNA) banana bunchy top virus (BBTV), family Nanaviridae, genus Babuvirus which represents a satellite DNA component with 12 DNA sequences motifs. [232]

The disease is extremely difficult to eradicate or manage. The virus leads to dark green stripes on leaf stem, followed by stunted growth and the decay of the fruit production No cure for the virus has yet been discovered. Some control can be achieved by killing the aphids which spread the virus. The banana aphid, which acquires the virus feeding on an infected plant in 4 to t8 hours, retaining the virus through its adult life. Control of banana bunchy top is achieved by killing the banana aphids and destroying all infected material. Infected banana plants can be first sprayed with an insecticide like Sevin, or simply soapy water. Sevin, the trademark of Carbaryl (1-naphthyl methylcarbamate) is a chemical in the carbamate family used chiefly as an insecticide.

Cucumber Mosaic Cucumovirus (CMV)

The cucumber mosaic cucumovirus is also spread by the banana aphid, though it does not spread as rapidly as BBTV, nor does it cause significant damage to banana fruit. Symptoms include flower mottling and streaking. [233]

Anhalt and Almeida 2008 found that adult aphids transmitted BBTV more efficiently at 25 and 30 degrees C than at 20 degrees C than third instar nymphs which, however were not influenced by temeprature variation. Both BBTV acquisition and inoculation efficiencies peaked after 18 h of plant access period and requires a latent period. [234]

Niu et al 2009 report that B3 and B4, encoded by DNA3 and DNA4 of banana bunchy top virus (BBTV), exhibit RNA silencing suppression activity to achieve infection of banana plant. B3 and B4 are the RNA silencing suppressors of banana bunchy top virus, increasing the pathogenicity of the virus and act at different steps in the RNA silencing pathways of the plant. [235]

Amin et al 2011 report that major pathogenicity determinants of BBTV pathogenicity are movement protein (MP) and cell-cycle link protein (Clink) as suppressors of RNA silencing of plant which is being invaded. [236]

The genome of Banana bunchy top virus (BBTV) consists of six segments of single-stranded DNA of approximately 1 kb in length. Yu et al 2012 sequenced the complete genomes of two BBTV isolates from Haikou, Hainan, China. BBTV could be grouped into two large groups, the Southeast Asian group and the Pacific-Indian Oceans group. Both the Haikou-2 and Haikou-4 isolates belong to the newly proposed Southeast Asian group. [237]

Recombination in the banana bunchy top virus genome

Stainton et al 2012 report that DNA-U3 components of the banana bunchy top virus (BBTV) present inter- and intra-component recombination, but all of the South Pacific DNA-R components have a common intra-component recombinant origin. The DNA-U3 and DNA-M components display a greater degree of inter-component recombination than the DNA-R, -S, -C and -M components. [238]

Intergenomic recombination in DNA-U3 among the isolates of two sub-groups of BBTV indicates that such intragenomic recombination may have importance in the evolutionary process of BBTV genome. Hyder et al. 2011 stress that intragenomic recombination generate genetic diversity in the ssDNA viruses. [239]

Plastids in Plants, bacteria and Archaea

Plastids are organelles found in the cells of plants and algae. Plastids are responsible for photosynthesis, storage of products like starch and for the synthesis of many classes of molecules such as fatty acids and terpenes which are needed as cellular building blocks and/or for the function of the plant.

Plastids may differentiate into several forms:
Chloroplasts, green plastids, are responsible for photosynthesis. Chromoplasts,coloured plastids, produce pigment and storage. Gerontoplasts control the dismantling of the photosynthetic apparatus during cell aging. Leucoplasts, colourless plastids, are responsible for monoterpene synthesis. Leucoplasts can differentiate into more specialized plastids: Amyloplasts, are responsible for starch storage and detecting gravity. Elaioplasts store fat. Proteinoplast/aleuronoplasts store and modify protein.


Plastid transformation increase plant stress resistance [240]

To increase plant resistance to drought, salinity, and extreme temperatures Bansal et al 2012 developed transplastomic plants with such properties. A transplastomic plant is a genetically modified plant in which the new genes have not been inserted in the nuclear DNA but in the DNA of the chloroplasts. The major advantage of this technology is that in many plant species plastid DNA is not transmitted through pollen, which prevents gene flow from the genetically modified plant to other plants [241]. The plastid transformation vector contains an aadA gene that encodes resistance to spectinomycin as a selectable marker of the acquired abiotic stresses tolerance. The authors stress that transplastomic technology is useful to increase abiotic stress tolerance in plants.

According to Rigano et al. 2012 the plastid genetic engineering, to overcome limitations, must include systems for species other than tobacco, develop the expression of transgenes in non-green plastids and increase accumulation of proteins. [242]

The small genome of chloroplasts of land plant included non-bacterial proteins durin evolution [243]

Chloroplasts in land plants have a small genome of only 100 genes. Their function is thought to rely on a cyanobacterium-derived system together with a hybrid transcription machinery containing non-bacterial proteins which was introduced during plant evolution.

P(II) signal transduction proteins and nitrogen regulation [244]

The P(II) proteins are signal transduction proteins implicated in the nitrogen metabolism in bacteria and archaea, and are also found in the plastids of plants. P(II) proteins interacts with enzymes, transcription factors and membrane transport proteins. Huergo et al.2012 explain how the key effector molecules, 2-oxoglutarate and ATP/ADP, influence the activities of P(II) proteins. P(II) is being regulated by 2-oxoglutarate. P(II) responds to changes of cellular energy status and carbon and nitrogen sources in cyanobacteria and regulates cellular metabolism. [245]

According to Radchenko and Merrick 2011, the PII proteins bind the key effector metabolites 2-OG (2-oxoglutarate), ATP and ADP. The action of P(II) is related to the crystal structures of PII proteins complexed with some of their target proteins, in addition to ATP/ADP- and 2-OG-binding sites. This interaction is reinforced by flexible T-loops of PII. The effector molecules influences the T-loops and regulates theinteractions between PII and its targets. [246]


Bacterial canker on kiwifruit

The bacterial canker on kiwifruit caused by Pseudomonas syringae pv. actinidiae is a severe threat to production of green-fleshed kiwifruit (Actinidia deliciosa) and yellow-fleshed kiwifruit (A. chinensis). Renzi et al. 2012 describe the kiwi disease spreading in Italy. [247]

The bacterium can infect host plants by entering natural openings and lesions, such as lenticels. One year after the first signs are found on leaves, the bacteria causes reduced ring width, a drastic reduction in vessel size, tyloses, and cambial dieback which occurs during the growing season.

Bacterial canker on kiwifruit, a pandemic disease [248]

Scortichini et al. 2012 classifies the global re-emerging wave of this disease as a pandemic resulting in enormous economic losses. The bacterium is Gram-negative, aerobic, motile, rod-shaped, polar flagella, oxidase-negative, arginine dihydrolase-negative. Worldwide there are four genetically different strains of Pseudomonas syringae pv. actinidiae distributed worldwide with varying pathogenicity to the plant. First signs of the disease are brown-black leaf spots often surrounded by a chlorotic margin.

Marcelletti et al.2011 analysed the genetic sequences of Pseudomonas syringae pv. actinidiae (Psa) outbreaks in Japan 1984 (J-Psa), in Italy 1992 (I-Psa) and the recent epidemic of the strain I2-Psa in Italy. The genomic sequences of J-Psa and I-Psa were very similar, however, the recent I2-Psa genome differs significantly from the samples of 1984 and 1992. The authors concluded that I2-Psa strain did not evolve from J-Psa and I-Psa, but represents a recent independent pathovar evolution. All strains are copper resistance, antibiotic detoxificating, have high affinity iron acquisition and detoxification of nitric oxide of plant origin. [249]

Highest losses of kiwi caused by MLSA Psa3 group of Pseudomonas syringae pv, actinidiae [250]

Pseudomonas syringae pv. actinidiae (Psa) presents at least four Psa MLST MLSA groups spreading worldwide. According to Chapman et al. 2012, the MLSA group Psa3 is the strain causes the formation of cankers, production of exudates, and cane and shoot dieback in kiwi plantations. MLSA group Psa4 was detected in New Zealand and Australia. However, the MLSA group, Psa3 causes worldwide the highest losses.

China is the probable origin of the recent bacterial canker of kiwifruit outbreaks [251]

Strains from China, Italy, and Portugal have been found to belong to the same clonal lineage. New Zealand isolates belong to the same lineage as the Italian and Chinese strains. The authors stress that their results suggest a movement of the pathogen between countries being Chinese the probable origin of the European and New Zealand outbreaks. The Japanese and Korean strains belong to a separate genetic lineage.


US prohibition of importation of kiwi plants [252]

The US Animal and Plant Health Inspection Service (APHIS) prohibits the importations of kiwi plants for planting (including pollen but excluding fruit and seed) hosts of P. syringae pv. Actinidiae (bacterial canker of kiwifruit) from all countries since 2010.

Integrated Pest Management (IPM)

[253] Integrated Pest Management (IPM) is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interaction with the environment. This information, in combination with available pest control methods, is used to manage pest damage by the most economical means, and with the least possible hazard to people, property, and the environment.

An American IPM system is designed around six basic components: [254]
  1. Acceptable pest levels: The emphasis is on control, not eradication. IPM holds that wiping out an entire pest population is often impossible, and the attempt can be expensive and environmentally unsafe. IPM programmes first work to establish acceptable pest levels, called action thresholds, and apply controls if those thresholds are crossed. These thresholds are pest and site specific, meaning that it may be acceptable at one site to have a weed such as white clover, but at another site it may not be acceptable. By allowing a pest population to survive at a reasonable threshold, selection pressure is reduced. This stops the pest gaining resistance to chemicals produced by the plant or applied to the crops. If many of the pests are killed then any that have resistance to the chemical will form the genetic basis of the future, more resistant, population. By not killing all the pests there are some not resistant pests left that will dilute any resistant genes that appear.
  2. Preventive cultural practices: Selecting varieties best for local growing conditions, and maintaining healthy crops, is the first line of defence, together with plant quarantine and 'cultural techniques' such as crop sanitation (e.g. removal of diseased plants to prevent spread of infection).
  3. Monitoring: Regular observation is the cornerstone of IPM. Observation is broken into two steps, first; inspection and second; identification. Visual inspection, insect and spore traps, and other measurement methods and monitoring tools are used to monitor pest levels. Accurate pest identification is critical to a successful IPM program. Record-keeping is essential, as is a thorough knowledge of the behaviour and reproductive cycles of target pests. Since insects are cold-blooded, their physical development is dependent on the temperature of their environment. Many insects have had their development cycles modelled in terms of degree days. Monitor the degree days of an environment to determine when is the optimal time for a specific insect's outbreak.
  4. Mechanical controls: Should a pest reach an unacceptable level, mechanical methods are the first options to consider. They include simple hand-picking, erecting insect barriers, using traps, vacuuming, and tillage to disrupt breeding.
  5. Biological controls: Natural biological processes and materials can provide control, with minimal environmental impact, and often at low cost. The main focus here is on promoting beneficial insects that eat target pests. Biological insecticides, derived from naturally occurring microorganisms (e.g.: Bt, entomopathogenic fungi and entomopathogenic nematodes), also fit in this category.
  6. Responsible Pesticide Use: Synthetic pesticides are generally only used as required and often only at specific times in a pests life cycle. Many of the newer pesticide groups are derived from plants or naturally occurring substances (e.g.: nicotine, pyrethrum and insect juvenile hormone analogues), but the toxophore or active component may be altered to provide increased biological activity or stability.
IPM programmes include diseases, weeds, and other pests that interfere with the management objectives of sites such as residential and commercial structures, lawn and turf areas, and home and community gardens.


The Massachusetts IPM Guidelines [255]

The Massachusetts IPM Guidelines present strategies of best management practices of protection of a series of plants The guidelines for most crops have been tested and adjusted through the USDA Farm Service Agency ICM cost-share program and through the Partners with Nature program. According to the UmassExtension of the University of Massachusetts Amherst, the guidelines can be used as a checklist for farmers to improve their pest management, document that IPM is practised on the farm, and may be used as an IPM educational tool to farmers, government officials and other groups. The guidelines are available at http://www.umass.edu/umext/ipm/publications/guidelines/index.html

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