Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Eggplant Insect PestsA female may lay more than 50 eggs. Eggs are greenish, banana-shaped and less than 1 mm long. Theyare embedded in one of the large leaf veins or in the leaf stalks. Hatching occurs after about 6 to 10days.There are 5 nymphal instars; the fully-grown nymphs are yellowish-green, frog-like and about 2 mm long.Nymphs are found on the underside of leaves during the daytime. The nymphal period lasts 14 – 18days. In warm climates, several generations occur.Host rangeJassids occur on most types of plants. Different species attack a variety of vegetable crops includingeggplant, tomato, okra, beans, lettuce, and squash.Plant damage and compensationThe jassid species Cestius phycitis is particularly harmful in eggplant because it can transmit theeggplant little leaf disease. Some species transmit mosaic virus.Jassids suck the plant sap and cause the edges of leaves to become yellow, with an upward rolling,giving a spoon-like appearance. Outer leaf areas appear yellowish or burned. Leaves are extremelysmall and show mosaic pattern, small whitish spots or yellowing. Fruit set may be very low.In the case of heavy attacks, the yellowed foliage turns brown and dies, and this may lead to a seriousloss in production. Leaf browning due to jassid damage is also called hopperburn.The insect population is greatest during the hot, wet season. The age of the eggplant does not seem toaffect the occurrence and multiplication of jassids.Natural enemiesFrom field studies in Bangladesh, some cases of fungal infectionof jassids have been reported. The exact species of this fungusis unknown at this stage, possibly Beauveria sp.Researchers from India reported that nymphs and adults of thejassid Amrasca biguttula biguttula collected from untreatedeggplant were found to be infested by larvae of predatory mitesof the genus Bochartia. (Ghai, 1975). Only the larval stage ofBochartia feeds on jassids; the adults and nymphs are free-livingpredators found in humus or among fallen leaves. Whether thispredatory mite species has potential for biocontrol needs to befurther studied.Jassid infected with Beauveria sp.Parasitoids Anagrus flaveolus and Stethynium tridavatum have been used to kill leafhopper eggs onother crops (ref. www35).Management and control practicesPrevention activities:• Resistant and tolerant varieties of eggplant have been reported. See table in section 3.2.2. Checkwith local seed suppliers for such varieties or set up a field trial to study differences in jassid (andother pests and disease-) susceptibility among eggplant varieties. Cultivars with hairy leaves arereported to be less susceptible to damage.• In studies from India, jassids populations in eggplant were highest in the middle of February and firstweek of August (Suresh, 1996). Where jassids are a serious problem changing planting dates, byplanting eggplant when the environment is less suitable for jassid multiplication, e.g. during winter,may be an option to reduce jassid infestation. This was confirmed in field studies carried out inAssam, India. Eggplant planted at the end of October had the lowest incidence of the jassid Amrascabiguttula biguttula (Borah, 1994).• Fertilization may have an influence on the infestation of jassids. In studies on eggplant carried out inIndia, an increase in the doses of nitrogen and phosphorus resulted in heavier infestation by bothjassids and fruit and shoot borer, but increased doses of potassium resulted in lighter infestation(Chaudhary, 1987). Fertilization and the effect on pest and disease occurrence and on yield can betested in a field trial. See section 3.8.82Eggplant Ecological Guide