FREQUENTLY ASKED QUESTIONS
AccoISR is usually initiated as a result of beneﬁcial microbes applied to the roots of the plant and increases the level of jasmonic acid in the plant tissues. Beneﬁcial microbes that are applied to the canopy usually induce SAR and it tends to increase the level of salicylic acid in leaf tissue.rdion Sample Description
AccorBiopesticides are more eﬀective when used in a prophylactic preventative programme, not dependent on thresholds or scouting. The colonization of the rhizosphere by beneﬁcial microbes in advance of the attack by pathogens and pests will reduce the living space on the roots where the pathogens might attempt to colonise. Beneﬁcial microbes will secrete substances, which can slow down the growth of the competing pathogenic microbes or kill them. This will reduce the level of disease or pest attack on the plant.dion Sample Description
Real IPM Trichoderma is Registered in Kenya and Ethiopia for the control of root knot nematode. Its probable mode of action is the excretion of a chitinase enzyme, which destroys the egg masses of nematodes on the outside of the plant roots. A root gall contains one large single female nematode. She extrudes eggs masses on the outside of the root and then dies. The gall will not disappear and remains as historical evidence of rkn presence. If Trichoderma is applied regularly with the irrigation water, the number of new galls should decrease.
Trichoderma is an endophyte and needs to be applied to re-growth of rose plants (red leaves) after ﬂushing or pruning. Downy mildews are also systemic which makes them diﬃcult to control because they are not exposed to control agents. Systemic fungicides are more prone to resistance occurring and Trichoderma should be tank mixed when systemic fungicides are applied – as part of a resistance management programme. Weekly foliar applications of Trichoderma have provided good control of downy mildews in roses and onions. Do not spray to ‘run-oﬀ’.
Scientists have measured a peculiar interaction between a plant under attack from a disease in the canopy. Root colonization by Bacillus subtilis increases (below right). The increased level of Bacillus subtilis on the root system sends signals to the plants own chemical pathways that produce abscisic acid and salicylic acid which are involved in controlling the closure of stomata. When stomata close they reduce the entry points for the disease into the plant.
Bacillus subtilis is known to produce lipopeptides, which destroy the cell membrane of powdery mildew spores on the leaf surface. (ref AgraQuest). These substances are produced by Bacillus during the manufacturing process and are present in the total fermented product. The live bacterium itself is less important than the substances in the liquid culture. Applications should not be made to ‘run-oﬀ’ so that the natural active ingredients remain in contact with the leaf surface and prevent powdery mildew spores form germinating.
Real Trichoderma and Real Bacillus subtilis are endophytes. Real IPM is currently inves-tigating the endophytic attributes of its EPFs (Metarhizium and Beauveria).
Phytopathogens are bacteria or fungi, often with part of their life cycle in the soil, which cause harm to the plant. Diseases are caused by phytopathogens. Endophytes colonize an ecological niche similar to that of phytopathogens, which makes them suitable as bio-control agents
An endophyte is a bacterium or fungi able colonize the internal tissue of a plant without causing a disease or any harm to the plant. Of the nearly 300,000 plant species that exist on the earth, each individual plant is host to one or more endophytes.
Rhizobacteria can form bioﬁlms on root surfaces; a continuous colony of bacteria bound together by polysaccharides. This helps the bacteria bind to the root surface and makes it more diﬃcult for other rhizobacteria to establish on the root. Bioﬁlm formation is enhanced by the presence of malic acid, which is excreted by plant roots.
Green manure crops act mainly as soil acidifying matter to decrease the alkalinity pH of alkali soils by generating humic and acetic acids. Incorporation of cover crops into the soil allows the nutrients held within the green manure to be released and made available to the succeeding crops. This results immediately from an increase in abundance of soil microor-ganisms from the degradation of plant material that aid in the decomposition of this fresh material. Microbial activity from incorporation of cover crops into the soil leads to the formation of fungal mycelium and viscous materials, which beneﬁt the health of the soil by increasing its soil structure by aggregation. The increased percentage of organic matter improves water inﬁltration and retention, aeration, and other soil characteristics
Green manure crops uprooted or mown crop parts, which are left to wither on a ﬁeld so that they serve as a mulch and soil amendment. Plants used for green manure are often cover crops grown which are ploughed under and incorporated into the soil while green or shortly after ﬂowering. Green manure is commonly associated with organic farming and can play an important role in sustainable annual cropping systems
The mycorrhizae network in the soil may provide a physical structure for the Trichoderma and Bacillus to grown on. Mycorrhizae are usually only applied once at plant establishment and both Trichoderma and Bacillus are applied regularly as crop protection agents and bio-fertilisers.
Mycorrhizae are an extension of the plant’s root system and the Trichoderma and Bacil-lus subtilis solubilise phosphate, create a larger physical plant root with more branches and are antagonistic against plant pathogens and pests.
Mycorrhizae spores remain dormant if phosphorous levels are above 70 ppm, however if you establish your mycorrhizae colony early on when phosphorous levels in the nutrient solution are lower, they may continue to grow later in the cycle when P levels are higher.
Ecto-mycorrhizae form a sheath around the plant roots and mainly colonise conifers and oaks. Endo -mycorrhizae (vesicular arbuscular mycorrhizae – VAM) will penetrate the root with a structure that enable exchanges to take place between the mycorrhizal network and the plant. Most vegetables, grasses, ﬂowers, shrubs, fruit trees and ornamentals associate with VAM.
Mycorrhizal fungi attach to the surface of the root and penetrate in or around the inside of the root cells. Filaments (called mycelium) extend into the surrounding soil, eﬀectively extending the plant’s roots and root absorbing capacity for nutrients and water, from ten to several thousand times. In return, the mycorrhizae receive from the plant roots sugars and other compounds. The mycorrhizal mycelium release enzymes that dissolve tightly bound minerals like phosphorus, sulphur, iron and all the major and minor nutrients used by plants. The nutrients are organically assimilated by the mycorrhizae and become readily available for use by the plants. The fungal ﬁlaments also bind soil particles into larger aggregates with organic glues such as humic com-pounds; the resulting soil structure allows air and water movement into the soil, encouraging root growth and distribution.
The galls of rkn are swellings within the root, which cannot be rubbed oﬀ by hand (below right) and Rhizobium nodules are external balls which can be rubbed oﬀ by hand (below left). If the Rhizobium nodules are actively ﬁxing nitrogen they will be pink in colour when dissected.
Even among rhizobia that can nodulate the same plant, there are many diﬀerent, geneti-cally distinct, strains. Some ﬁx nitrogen better—more eﬃciently—than others, resulting in superior plant growth. Some also compete better with rhizobia that are already in the soil. This means that they can enter the plant’s root hairs more eﬃciently, resulting in faster nodule formation. Commercial Rhizobia strains have been developed for speciﬁc legumes (peanuts, cowpeas, clover etc.)
The ﬁxed N2 is released when the plants die, making it available to other plants and this helps in fertilizing the soil. If the legume crop debris is removed from the ﬁeld there is less beneﬁt because most of the nitrogen is in the leafy and fruiting parts of the legume plant.
Legumes can ﬁx more than 250 kg N per hectare. However, the amounts of N2 ﬁxed can vary considerably depending on pesticide applications to the soil, presence and eﬀectiveness of rhizobia, pest damage, plant genotype and age, plant and rhizobia interactions and changes in soil physiochemical conditions. Nitrogen is an important building block of proteins and the seeds of legumes (beans and peas) are valued for their high protein contents.
A symbiotic relationship between the plant and the microbe requires both the plant and the microbe to beneﬁt. This requires some compromises to take place. For example: For the plant to be able to beneﬁt from the added available nutrients provided by the rhizobacteria, it needs to provide a place and the proper conditions for the rhizobacteria to live. Creating and maintaining root nodules for rhizobacteria can cost between 12–25% of the plants total photosynthetic output.
Plants are able to shape their rhizosphere microbiome by secreting diﬀerent exudates attractive to diﬀerent soil microbes. Diﬀerent plant species host speciﬁc microbial communities when grown on the same soil. Rhizobium colonise legume roots but not other types of plants.
Some PGPRs produce phytohormones (e.g. auxin), which promote the formation of later-al roots. Increased lateral root formation leads to an enhanced ability to take up nutrients for the growth of the plant.
PGPR can (a) increase nitrogen availability to the plant (b) precipitate insoluble com-pounds from the soil and sequester these in their own cell components – thereby cleaning up heavy metal pollution in the soil (c) migrate form the rhizoplane to the rhizosphere where they can bind ions in biologically unavailable forms (d) assist in the formation of iron-chelating siderophores to improve the ﬁtness of plants by increasing iron uptake. (e) reduce the intake of sodium into the plant and avoiding sodium toxicity in high saline soils (f) increase the availability of nutrients to the plant by production of organic acids that change the pH of the soil near the root.
Rhizobacteria are root-colonizing bacteria that form symbiotic relationships with many plants. The name comes from the Greek rhiza, meaning root. Though parasitic varieties of rhizobacteria exist, the term usually refers to bacteria that form a relationship beneﬁcial for both parties (mutualism). The relationship of PGPRs with host plants are either rhizospheric (limited to the outside of roots) or endophytic (within the host tissues). Biostimulants = PGPR = Biofertilisers.
Roots release nutrients made up of organic acids and inorganic hydrocarbons that microbes use as a food source. Soil microbes will colonise hot spots on the roots surface where they can feed on sloughed-oﬀ root cap and border cells, mucilage, and plant exudates.
Whilst there is some secondary pick of EPF spores by host insects passing by spores previously deposited on the leaf by commercial spray applications – this is of minor signiﬁ-cance compared to direct application of the spores onto the host insect’s body. This requires optimum application coverage and application at a time of day when the pest is exposed to spray coverage (on top of the leaf)
The parasitic wasps have defense mechanisms, which protect them from infection by EPFs. The EPFs tend to be very speciﬁc in their target pest and parasitoids come from very diﬀerent insect families to most pests. Parasitoids often have the ability to distinguish between hosts that are infected or not infected by EPFs and avoid coming into contact with the EPF.
If the EPF is being used in an auto-dissemination device and is relying on the host to re-distribute the EPF within the pest population – the ADD is more eﬃcient, the longer it takes for the contaminated pest to die. The infected pest will come into contact with more pests, the longer it lives and more pests will receive EPF spores. (see FAQ on ADD).
The speed of death depends on the application rate of the biopesticide, the temperature and the susceptibility of the pest to that particular isolate of the biopesticide. It may take 3 to 10 days for the pest to die, but during this period it may feed less on the crop plant and lay fewer eggs.
The spores of an entomopathogenic fungus must land on a target pest, which it recog-nizes as a host before it will even germinate. Once it has germinated, it will grow over the surface of the host in search of a soft area where it is easier to penetrate the insect pest. It then forms a special structure, called an appressorium, which helps it to drill down and enter the pest’s body. Once inside the pest, it must be able to overcome the pest’s own immune system in order to enter the insect’s haemolymph. The insect’s haemolymph is full of nutrients, which feed the EPF allowing it to grow. In the process of growing, the EPF gradually kills the pest and eventually the fungus grows and sporulates on the outside of the dead insect.
Although biopesticides are killed by UV light (after two days), for practical reasons they need to be applied at any time of day when a chemical would have been applied. It is more important to apply the EPF when the pests are active in the crop and can be targeted by the biopesticide spray. Nocturnal pests (weevils and moths) should be sprayed at night. Fruit ﬂies should be sprayed between 9 and 1 am and 4 and 5 pm. Thrips should be sprayed within two hours of sunrise and within 2 hours of sunset when adults congregate on the outside of ﬂowers and the upper surface of leaves.
If the temperatures are low and the crop is dormant, the life cycles of the pests and diseases are probably also ‘dormant’. In which case, it is probably not cost eﬀective to continue applying the biopesticide/biofertiliser. However, the farmer should monitor soil temperatures and soil moisture levels and should consider stopping biofertiliser/ biopesti-cide applications to the soil if the winter soils are too wet to sensibly apply irrigation water or the soil temperatures are below 5 deg C. Once the spring soils begin to dry out and the soil temperatures rise above 5 deg C, the farmer may consider re-starting the regular soil application programme.
The lower the level of organic matter in the soil – the more frequently the biopesticide should be applied. Both EPFs and Trichoderma can grow saprophytically on organic matter in the soil.
Yes. The biopesticides will colonise the roots of the crop, even in pumice grown crops. There will also be some dead roots (organic matter), which will be a substrate for saprophytic growth of the beneﬁcial microbes. Weekly applications are recommended. If this is too expensive – apply half rate doses.
The frequency may depend on the economic impact of the pest or disease. If there is serious economic impact from the pest/disease, a weekly application is cost eﬀective and ensures persistence of high levels of the biopesticide where it is needed. At the other extreme, where the pest or disease is already reasonably under control – a monthly application may be suﬃcient.
The soil is the natural habitat of a biopesticide and it may persist for several months, declining in concentration over this time because of strong competition from other microbes and soil insects that feed on fungi in the soil. However, the declining biopesticide microbe population in the soil may not provide as eﬀective crop protection against soil pests and diseases. So regular weekly applications may be necessary to provide the required level of crop protection.
A biopesticide spray may not survive more than about 12 to 48 hours if it is exposed to the UV in sunlight in the canopy or very hot and dry conditions. However. If the spray comes into contact with the target pest and recognizes the host – it will germinate, penetrate and infect the inside of the pest, where it is immediately protected from the harmful eﬀects of challenging environmental conditions. If the spray is directed eﬀectively to the under leaf surface on the lower part of the canopy the EPF can sometimes be seen growing on the pest cadaver (dead body). In the absence of the host, the EPF will not establish and grow on leaves.
Amblyseius cucumeris: Ist instar thrips juveniles and in the absence of thrips it will prey on spider mites and feed on pollen. Amblyseius swirski: Does best when both thrips and whiteﬂy are present at the same time but reproduces slowly if only one pest is present; Amblyseius californicus: spider mites in hotter dry conditions than Phytoseiulus prefers; Amblyseius montdorensis: preys well on spider mites, thrips and whiteﬂy but prefers higher humidity than A. californicus. Is the only Amblyseius to eat 2nd instar thrips and eats more whiteﬂy, thrips or spider mites per day than the other Amblyseius spp.
There are no risks of this happening with the use of predatory mites produced by Real IPM. None of the predatory mites feed on plants. Phytoseiulus is very speciﬁc in the pest mites that it can feed on and will prey on other Phytoseiulus eggs and juveniles if spider mites are not available. Although Amblyseius spp can also feed on pollen, they cannot reproduce well without their preferred prey.
Planting all the same plant in one place (a crop) already upsets the ‘balance of nature’ and has attracted certain insects which feed on it and reproduce in it – upsetting the ‘balance of nature’ again. Using predatory mites in large numbers is necessary to regain control by eliminating the pest.
By tank mixing biopesticides with chemical pesticides, the farmer is in eﬀect designing a new ‘formulation’ of the chemical pesticide because of the addition of the many other modes of action supported by the biopesticide.
Biopesticides diﬀer from chemical pesticides as far as ‘resistance management’ is concerned because beneﬁcial microbes have so many diﬀerent modes of action and produce a wide range of natural chemicals. Chemical pesticides are usually just one ‘active ingredient’, which makes it much easier for a pest or disease to develop resistance to this. There are no recorded incidences of resistance developing to a biopesticide – therefore they can be routinely sprayed and do not have to be ‘rotated’ with other active ingredients’ in the same way as it is necessary to rotate chemical active ingredient to avoid resistance.
Chemical pesticides generally only have one ‘active ingredient’. If the same chemical pesticide is applied too frequently – the pest or disease has the opportunity to develop ways to deactivate the pesticide’s chemical pathway. As the number of resistant pests and disease spores increase – resistance develops in a ﬁeld population. See: www.frac.info and www.irac-online.org