Subsections

Phytopathology, diseases of plants

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[1450].
Phytopathology wants to bring a bectter understanding on the cause, the circumstances and the progress of diseases of plants as well the interaction of host-pathogenic agent.
Phytopathogenic agents are not pathogenic to mankind as moulds and bacteria known as phytopathogenic cannot grow at 37$^{o}C$ 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.

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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

[1278]
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 teres:Disease 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 flavus:Disease 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 zeae:Disease 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 B$_{1}$. 100mcg in the feed of mice over a long period o time induces liver cancer in all rats. In Africa Aspergillus flavua can be very high. The disease of liver cancer is in Africa the highest of the world because of contaminated 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.[1473]
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 avoided by getting the plantations one to one and a half meter under water. After six month 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. 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

[1474]
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 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. [1475]

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.

Garlic white rot on organic muck fields

[1476]
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$^{o}C$ and will remain remain in this range for approximately 3 months with good uniform spread of the stimulant.


Biologic control of the invasive chilli thirps, Scirtothrips dorsalis

[1477]
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

[1478]
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

[1479]
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

[1480] [1481]
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) [1482] and pondspice(Litsea aestivalis, L.) [1483].

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 [1484].

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.

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. [1485]

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. [1486]

Fighting crop pests and drought

[1487]
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.

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.

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

[1500] 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

[1974]

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. []


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.


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.


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

[1525]
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

[1526]
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

[2320]
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

[2321]
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

[2319]
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. [2322]

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". [2323] [2324]

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

[2325]
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. [2350]

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. [2352]

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: [2351]

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.

\includegraphics[width=260.56bp,height=250.67bp]{library/Corn.eps} 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

[2353] [2354] 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.
\includegraphics[width=251.56bp,height=238.67bp]{library/flowers.ps} 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 [2355]. 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

[2356] 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

[2356]
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:

[2356]
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:

[2356]
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

[2356]
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

[2356]
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

[2357]
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

[2357]
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$^{o}C$ for three hours, to kill insect eggs and larvae.

The biologic control of moths

[2361]
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

[2358]
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) [2359].

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 [2360].

The Spotted Wing Drosophila fruit fly emerging fruit pest

[2362]
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. [2363]

Biologic control of the corn stem borer (Chilo partellus)

[2361] [2364] [2365]
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.

[2366]
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. [2367]

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. [2368]

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. [2368]

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. [2368]

Citrus greening also known as huanglongbing

[2370] 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$^{0}C$, while a temperature of 32$^{0}C$ 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.

Iceberg lettuce breeding for high resistance to fungus and microbes

[2369] [2371] 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 made seeds of three new parent lettuces available to researchers and plant breeders the parent lines are meant for crossing with consumer-ready lettuces to boost the commercially grown lettuces' resistance to verticillium wilt.

Verticillium wilt

The Verticillium dahliae fungus infects roots of vulnerable plants, moving into leaves and causing them to discolour, then to eventually wilt and die. The fungus can also infect and kill hundreds of other kinds of plants, including strawberries and tomatoes.

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.

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 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. [2372]

Lupinus polyphyllus Lindl. is a perennial ornamental belonging to the Leguminosae family. It is grown in gardens for flower beds and borders. Garibaldi and colleagues found the fungus Verticillium dahliae to infect up to 30% of this legumonose in Northern Italy. [2373]

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. [2374]

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. [2375]

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. [2376]

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. [2377]

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. [2378]

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 [2379]

Insect pest control using nematodes

[2380]
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

[2381]
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

[2382]
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

[2383]
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

[2384]
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. []

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

[2386]
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

[2387]
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

[2388]
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

[2389]
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. [2390]


Red palm weevil may pose a risk to date production

[2391]
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: [2392]
  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

[2393]
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

[2394] Leaf-cutting ants such as Atta sexydens and Acromyrmex octospinosus live in Argentina, the south of Brazil including the state of Sao 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. [2395]

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

[2396]
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

[2397]
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

[2398]
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. [2399]

Yeasts associated with leaf-cutting ants

[2400]
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

[2401]

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. [2402]

Phorid flies

[2403]
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. [2404]
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. [2405] [2406]

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

[2407]
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.

Trees emit isoprene linked to aerosol formation

[2408]
Paulot and colleagues 2009 write that trees emit isoprene which represents 40% of nonmethane hydrocarbon compounds released to the atmosphere. Isoprene comes only from plants. It is readily oxidized first to hydroxyhydroperoxides, then to dihydroxyepoxides. Nearly 100 million tons of epoxides carbon are released to the atmosphere per year. The authors report that epoxides are the link between the degradation of isoprene to organic aerosols. Epoxides reacts with acids in the atmosphere to become a glue sticking to particles which make up the particulate of the air we breath. In crowded areas the OH acidic radical content of the air is high increasing the particulate formation in cities.

The authors point out that some trees produce more isoprene than others, while oaks produce the most of it. South Coast Air Quality Management District in Southern California regarded the organic carbon compound emission of trees and published a list of low emission trees. The emission of isoprene should be considered when planting big monocultures of trees.

A group around Dr. Allan Drew and Dr.Richard Smardon of the State University of New York College of Environmental Science and Forestry performed a study determining the best tree combination to remove carbon dioxide and reduce the emission volatile organic compounds which contribute to the formation of ozone in air. The group recommend trees with denser wood such as hawthorn trees for best carbon-sequestring ability. Disease susceptible trees such as the American elm should be avoided. A group of 31 trees were found to provide best results, including dogwood, red hickory and hawthorn. [2409]

Aerosol emission of the Amazon forest

[]
Graham and colleagues in a study of 1999 report that the Amazonia represents one of the most important sources of organic atmospheric aerosols, with organic matter accounting for up to 90% of the total aerosol mass. The aerosols were vegetation detritus, pollen and the photo-oxidation products of volatile biogenic organic compounds. Deforestation by slash-and-burn add large quantities of smoke aerosols into the atmosphere.

The emission of water soluble organic compounds within aerosols may potentially enhance the ability of aerosols to nucleate cloud droplets, and influence their chemistry. These changes alter the radiation balance and hydrological cycle and may influence global climate.

The authors stress that many polar, oxygenated compounds were identified. Anhydrosugars, produced from the combustion of plant polysaccharides were the main compounds identified in the dry season samples. Levoglucosan, a cellulose breakdown product, is found in concentrations as high as 5 microg m-3.

Sugars and sugar alcohols were found by the authors as main aerosol species in the wet season such as arabitol (6 ng/$m^{3}$), manitol (5 ng/$m^{3}$) and alfa and beta-glucose (2 ng/$m^{3}$).


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