CONSEQUENCE OF SOME INSECTICIDES ON PREDATOR COCCINELLA SEPTEMPUNCTATA

Abstract

Studies were undertaken in the field and laboratory to investigate the effects of some insecticides viz., Diazinon, Fenitrothion, Cypermethrin and Chlorpyrifos used against mustard aphid Lipaphis erysimi (Kalt) or the predator, Coccinella septempunctata L. during November 2004 to February 2005 at the Sher-eBangia Agricultural University farm, Dhaka. The experiment was laid out in a randomized block design and replicated five times. Insecticides were sprayed @ 0.05% on 27 December 2004 and on 12 January 2005. Records on the mortality of mustard aphid and toxic effect on the predators under the different treatments were made at I, 4 and 7 days after first and second spraying. The percent reduction of aphid infested plant, percent reduction of aphid population and percent reduction of the predator varied at different level of significant. The mortality of aphid, larvae and adult of the predator were significant at various levels. Mortality of the aphid reached highest after 24 hours of spraying. Cypermethrin was the most effective insecticide causing the highest mortality of mustard aphid and less toxic effect on the predator. Cypermethrin showed higher effectiveness than other three insecticides in increasing various growth parameters and seed yield of mustard. Considering benefit cost ratio (BCR), Cypermethrin was found to be the most economic and effective insecticide in controlling L. erysimi. and most safer for predator lady bird beetle.