Cumulative effects of insecticides on generalist predators and parasitoid population in cocoa ecosystem

摘要

Cocoa (Theobroma cacao L.) is a small under-storey tree endemic to the low land rainforests of the Amazon basin (Wood and Lass, 1985). Pests and diseases are the main constraints in cocoa production. Tea mosquito bugs known as mirids or plant bugs areserious pests of cocoa world wide (Entwistle, 1972). In India, cocoa is attacked by three species of tea mosquito bug viz., Helopeltis antonii Signoret, H. bradyi Waterhouse and H. theivora Waterhouse (Sundararaju, 1996). Among this, H. bradyi is the most predominant species attacking cocoa (CPCRI, 2011). It is a polyphagous sap sucking insect and both the nymphs and adults suck the sap from all parts of the cocoa plant. Salivary secretions are injected into the plant tissue which causes lesions on thecocoa pods, cherelles and flushing shoots. Estimates of crop loss attributed to damage by Helopeltis sp. are variable and depend on factors such as management practices, locality, climate and the plant and insect species involved. Chemical insecticidespredominate in the management of tea mosquito bug. A number of predators and parasitoids have been reported against Helopeltis spp. by several workers. They include ants, spiders and reduvid bugs (Ambika and Abraham, 1979; Devasahayam andNair, 1986; Sudararaju, 1996). Information on the effects of insecticides on predators and parasitoids in cocoa ecosystem is very limited. Therefore the present study was undertaken to assess the species composition and cumulative effects of insecticides spray on predator and parasitoid population occurring in cocoa ecosystem.