EFFECT OF DATES OF SOWING ON THE INCIDENCE OF JASSIDS, WHITEFLIES AND SHOOT AND FRUIT BORER OF OKRA

摘要

Okra, Abelmoschus esculentus (L.) Moench is grown extensively in the tropical and subtropical regions of the world. A number of insect pests, viz., leaf hopper (jassid), Amrasca biguttula biguttula (Ishida); shoot and fruit borer, Earias insulana (Boisd.) and E. vittela (Fab.); aphid, Aphis gossypii (Glov.); whitefly, Bemisia tabaci Genn. and leaf folder, Sylepta derogata Fab. cause extensive damage to different crop growth stages during June to September (Dadheech et al., 1977 and Kushwaha, 1983). The Jassids suck the cell sap from the lower surface of the leaves and inject some toxic material resulting in curling of leaves and stunted plant growth. Severe infestation causes burning of leaves which fall down later on. This results in drastic decrease in yield, i.e. 40-60 per cent. (Lal, 1940 and Narke and Suryawanshi, 1987). The aphids apart from acting as vector of plant diseases, secrete honeydew on the leaves due to which black sooty mould develops which hinders photosynthesis (Butani and Verma, 1976 and David and Kumaraswami, 1982). The larvae of shoot and fruit borer bore into the growing shoots, flower buds, flowers and fruits of okra either killing the plant or causing heavy shedding of fruits, resulting in drastic decrease in yield, i.e.35-76 per cent (Narke and Suryawanshi, 1987 and Hafeez and Rizvi 1994). The pest population fluctuates at various stages of crop growth and influenced by time of sowing due to ecological factors.