Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

_____________________________________________________________________Ecology of insect pests and natural enemiesLeaf compensation study results from Jessore, Bangladesh:A study was set up to determine if eggplants could compensate for loss of leaves. There were 6treatments for this trial, based on the probable infestation time of the important defoliators.25 and 50% leaf cut at 35 DAT (at plant establishment stage)25 and 50% leaf cut at 55 DAT (at pre-flowering stage)25 and 50 % leaf cut at 65 DAT (early fruiting stage)This resulted in the following data:A. 25 and 50% leaf cut at 35 DAT took 34 and 42 days respectively to compensate the loss of leaf.It was observed that more cut took more time to compensate.B. 25 and 50% leaf cut at 55 DAT took 21 and 35 days respectively to compensate for the loss ofleaf. It also implies that the plant at pre-flowering stage recovers quickly.C. 25 and 50 % leaf cut at 65 DAT took 25 and 35 days respectively to compensate for the loss ofleaf.The highest yield was achieved in the 25% leaf cut at 35 DAT treatment. This could be due to betterutilization of sunlight and less shading effect.Generally it was observed that the plants can compensate for defoliation quite well.(Kumar, TOT Jessore report, 1999)Similarly, when eggplant shoots are lost, for example due to feeding damage of fruit and shoot borerlarvae (FSB) the plant can also compensate for this loss by producing more shoots. Whether there is aneffect of shoot loss on yield depends on the growth stage in which the damage occurs. See box below.Shoot compensation study: an example from Jessore:In a compensation study in Jessore, Bangladesh, complete shoots were cut off the plant to simulatethe effect of the fruit and shoot borer (FSB), Leucinodes orbonalis. The shoot pruning was done asfollows:• Control – no shoot pruning• 20, 30 and 50% pruning at 75 DAT.• 20, 30 and 50% pruning at 100 DAT.In all treatments, the average number of branches, the plant height (125-142 cm), and leaf size (80-85 cm)were not significantly different. Fruit yield in all treatments varied from 3150-3270 kg/ha, but washigher in the 30% pruning at both 75 and 100 DAT.The group concluded that loss of shoots is not reducing the yield of eggplant significantly becausedamage to the shoots by FSB could be compensated for well by the plants.(Kumar, TOT Jessore report, 1999)Loss of leaves or shoots does not necessarily lead to production loss!It is important to remember that spraying for insects that are not causing yield loss is a waste of moneyand time, and it may cause needless health problems and environmental pollution.However, even small injury to fruits results in considerable loss of quality and inherent lower productprices.Set up a field study to find out how much defoliation/shoot loss at what growth stage your eggplantvariety can tolerate under local conditions without production delay or yield reduction.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:4.A.3. Plant compensation study52Eggplant Ecological Guide