Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________________Disease EcologyGliocladium virens (previously known as Trichoderma virens) was the first antagonistic fungus to getapproval of the Environmental Protection Agency (EPA) in the USA for registration. Trichoderma is oftenused as a spore suspension on carrier material such as rice bran. It can be used both as a preventiveand curative. However, application before pathogens are visible, as a prevention, always gives the bestcontrol.Trichoderma species are successfully used and multiplied in several countries in Asia, includingThailand, Philippines, Vietnam and Indonesia (FAO-ICP Progress report ’96 – ’99).Trichoderma sp. should be mixed into the soil a few days before (trans)planting.A negative effect of Trichoderma has been reported on mushrooms. Trichoderma cannegatively influence mushroom cultivation, possibly due to killing or inhibiting the mushroomfungi. More research is needed to study these effects, but in the meantime it is advisable notto use Trichoderma close to a mushroom production area (Harman, 1998).Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:3.5. Beneficials among the pathogen groups7.11 What about fungicides?Available fungicides and bactericides are often not effective enough to stop any of the major eggplantdiseases, especially during prolonged periods of wet weather. They can however, delay infection ofdiseases. Fungicides (if necessary) should always be combined with structural management methodslike crop rotation, sanitation, etc. (see section 7.8).7.11.1 Chemical fungicidesThere are several ways of classifying fungicides. An often used classification is the following:• Preventive fungicides: those should be applied before the disease actually occurs. The fungicide willform a protective layer around the plant which prevents spores from germinating on the plant. Timingof fungicide application is very difficult to predict. Also, when it rains, the fungicide will be washed offthe leaves and there is no protection anymore, just environmental pollution. There are products thatcan be added to the fungicide that help it stick better to the plants, these are called stickers. Resultsin practice however vary.• Curative fungicides: products that you can spray when symptoms of a disease occur. Some of theseform a layer around the plant (contact products), others are uptaken by the plants and transportedthrough the veins to other plant parts (systemic products).Good to know about fungicides:• There are few effective sprays against bacterial diseases!• There are no sprays against virus diseases! (usually insect vectors should be prevented fromentering the crop in areas where virus diseases are a problem).• Control of soil-borne diseases with fungicides is usually not effective: it depends on the pathogenhow deep below soil surface it can live and it is unclear how deep the fungicide will go. Somepathogens live inside plant left-overs in the soil, where they are protected from fungicides. From anenvironmental point of view, it is dangerous to apply fungicides to soil. What is the effect on thebeneficial micro-organisms that decompose plant rests? Will the pesticide contaminate the groundwater? How long will the pesticide persist in the soil?• Frequent use of fungicides may lead to fungus resistance to that type of fungicide. That means thefungus is no longer susceptible to the fungicide. For example, there are different “strains” ofFusarium wilt in tomato (Fusarium oxysporum). All of these Fusarium strains cause tomato wilt butthe genetic characteristics of a strain are slightly different. This is comparable with different varietiesof tomato: all of them are tomato but they differ in e.g. fruit size, color and maturity. Strains may differin susceptibility to fungicides.• Many fungicides can actually kill natural enemies of insect pests! For a study example, see box insection 4.9.128Eggplant Ecological Guide