Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________Major Natural Enemies of Eggplant Insect Pestsbe carried by wind or water, must contact the pest insect to cause infection. When insect-pathogenicfungi are applied, for example through a spore-solution, good spray coverage of the plants is essential.Primary or secondary ???When you leave a plate of food with, for example, some chicken meat in your kitchen for a few days,you may find the meat covered with fungus when you look again. This fungus is called a secondaryinfection: it was not the reason the chicken died (the chicken was probably killed for meat). Theinfection came in after the chicken was dead.Similarly, when insects are dead, some fungi may start growing on the dead insect. This is alsocalled a secondary infection. These fungi that cause secondary infection are part of the “trash menteam” of nature: they make sure dead things are decomposed quickly. When the fungi actually causea living insect to die, like insect-pathogenic fungi do, it is called a primary infection.Interesting, but why bother?When searching for beneficials in the field, it is important to distinguish between pathogens causingprimary infection and those causing a secondary infection. Insects with a secondary infection mayoften be already partly decomposed.Knowing that there is a fungus controlling pest insects in your field, should make you extra carefulwhen considering pesticide applications, especially fungicides. Fungicides can quickly kill thebeneficial fungi!How to use this…?When a primary infection is suspected and there are many insects dead and covered with fungus,you may consider making your own bio-insecticide from these dead insects. Collect as many as youcan find in the field, put them in a jar with water, crush them a little and stir firmly. This will releasefungus spores into the water. Filter the water slightly to remove large insect parts. The remainingsolution can be used to test its effectiveness in insect zoos. Spray the solution over insects that areplaced in a jar, or (better!) dip leaves into the solution and place it in the jar. Check if these insectsbecome infected over the next days. Use water as a control. See also box in section 4.9. If it works,similar solutions can be applied to the field. It might give additional control of pest insects.Free help from Mother Nature! ☺ConservationMany insect-pathogenic fungi live in the soil. There is evidence that application of some soil insecticides,fungicides and herbicides can inhibit or kill these fungi. For example, even very low concentrations ofsome herbicides can severely limit the germination and growth of Beauveria bassiana fungal spores insoil samples.6.3.3 VirusesBaculo viruses are pathogens that attack insects and other arthropods. Like some human viruses, theyare usually extremely small (less than a thousandth of a millimeter across), so they can only be seen withpowerful electron or light microscopes. There are two main types of Baculo viruses important for insectpest control:• Nuclear polyhedrosis virus (NPV) has been successfully used for the control of several caterpillarpests of vegetables including armyworms (Spodoptera sp.), tomato fruitworm (Heliothis armigera),diamondback moth (Plutella xylostella), and cabbage looper (Plusia sp.).• Granulosis virus (GV): have been found in several caterpillar species including cutworm (Agrotis sp.),armyworms (Spodoptera sp.), diamondback moth (Plutella xylostella), cabbage butterflies (Pieris sp.),cabbage looper (Plusia sp.), and the webworm (Hellula undalis).The majority of baculoviruses used as biological control agents are in the genus NPV. There are differentstrains (or “varieties”) of NPV and each strain is very specific to a target insect. For example HaNPV isNPV for control of tomato fruitworm Heliothis armigera (Ogrodnick, www7). No NPV specific to eggplantinsect pests has been found or developed to date. For more details on NPV please see TomatoIntegrated Pest Management: An Ecological Guide (FAO December 2000).113Eggplant Ecological Guide