Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

_____________________________________________________________________Ecology of insect pests and natural enemies4.6 A pest or not a pest insect…: how to find out!Many insects can be found in an eggplant field. Not allof them can be called “pests”, in fact, very few insectshave the potential to cause yield loss to eggplant. Thefew insects that do cause some yield loss in somefields in some seasons, are called “pest insects”. Asthe pest insects do not cause yield loss in all fields allthe time, a better term to use would be “herbivores”.Herbivores do not just eat plants or suck the plantjuices, they have an additional function: they serve asfood or as a host for natural enemies.There are many potential “pest insects” that do notbuild up in populations large enough to causeeconomic yield loss. They may eat a few leaves hereand there but this does not affect the yield or quality ofthe eggplant. In fact, their presence keeps the population of natural enemies alive so one could almostsay at that time they are “beneficial”....!The goal of growing eggplants is to produce as much yield as possible without spending a lot of money.If there are no pests to control, do not waste money on pesticides that can damage the natural enemypopulation, the environment and your personal health!When you find insects in the field, it is sometimes difficult to judge whether they are actually damagingthe plants or not. Some insects may just be crop visitors passing by and resting on the plants or on thesoil, or neutrals that live in the crop but do not eat from the plants nor influence the pest populations asnatural enemies directly. Neutrals can be a food source for natural enemies.When you find insects and you are not sure what they are: pests, natural enemies, or cropvisitors/neutrals, set up an insect zoo to find out what the function of that insect is. See box below.When you find that an insect is eating the eggplant leaves, it could be classified as a “pest insect”. Butagain, as explained above, not all plant damage results in yield loss. Thus, not all “pest insects” areactually “pests”!Whether or not a pest insect is a pest depends not only on the population of that insect but also on thegrowth stage of the crop in which it occurs. For example, the fruit and shoot borer (Leucinodes orbonalis)may cause some injury to leaves and shoots at the vegetative stage of the crop but, depending on theamount of injury, the plant can compensate for this by producing new leaves and shoots. However,during fruiting stage, larvae of the fruit and shoot borer attacking fruits cause direct quality loss of fruits.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:1.6. Show effects of beneficials incl. natural enemies4.1. Insect zoo4-A.4. Assessment of impact of ground-dwelling predators4-A.5. Measuring the parasitism level of caterpillars53Eggplant Ecological Guide