Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Eggplant Insect Pests♀♂Aphid reproduction: no males needed!?!Aphids can reproduce asexual: that means that males and females don’t have to mate in order toproduce young. One female gives birth directly to small nymphs. That means large numbers ofaphids can be produced in a very short time! Only in cool areas, eggs are produced after mating.The eggs overwinter and young nymphs emerge when the temperature rises.All winged aphids are females. In the tropics, most unwinged aphids are probably also femalesbecause most reproduction in the tropics will be asexual so males are not needed.Life cycleIn cooler areas, the aphid overwinters as small, shiny black-colored eggs laid particularly around leafscars of stems of plants that remain in the field throughout the winter. When the temperature rises, theaphids hatch and colonize the new emerging flowering stems or harvested vegetable crops that have notbeen ploughed in. Then, winged aphids fly away to colonize new host plants. They produce winglessaphids. These aphids produce more young aphids that form new colonies. They feed on the tender,actively growing shoots and leaves, often on the underside of leaves where they are protected from thesun and rain. When aphid numbers outrun food supply, winged forms reappear and migrate to nearbyplants to renew the growth cycle. This happens regularly during the growing season.Wingless aphid, winged aphid, and aphid colony on young leaves.(from: Stoll, 1987)In warm, tropical environment, aphids usually continue the asexual reproduction cycle without producingeggs. Warm, dry weather favors a rapid build-up of aphid colonies.Host rangeThe aphid is a serious pest of many vegetables and other crops like cotton. Some aphid species arespecific for one crop, e.g. the cabbage aphid only infests cabbage or other cruciferous crops. Aphids oneggplant are usually common species that infest many crops.Plant damage and plant compensationAphids can damage a crop in several ways:1. They suck plant sap. At high aphid populations, less sap with nutrients is left for the plant resulting inpoorer growth and lower production of fruits. Leaves wrinkle and can remain very small.2. They produce honeydew, which forms a sticky layer on the plant and fruits and make it ‘dirty’. Fungusmould can start growing on the honeydew.3. Aphids can transmit virus diseases (when there are winged aphids).4. Aphids (and their moulded skins) on products lowers quality and price.Aphids appear very localized: they usually colonize just a few plants but can be very abundant on oneplant.Natural enemiesThe weather is a major natural agent restricting the build-up of aphid infestation in cold, temperateregions and mountainous areas. In dry, warm seasons the population of aphids often rapidly builds upwhereas in wet, cool seasons the aphid population remains small. In a period of frequent rain, aphidpopulations will be very low if not absent.84Eggplant Ecological Guide