EFFECTIVENESS OF SOME INSECTICIDES FOR THE CONTROL OF MUSTARD APHID Lipaplais erysimi kalt. AND THEIR EFFECTS ON PREDATOR Coccinella septempunctata L.

Abstract

Studies were made in the field and laboratory condition to investigate the effects of insecticides viz.• Diazinon. Fenitrothion, Cypermethrin and Chlorpyrifos against mustard aphid Lipaphis erysirni (Kalt) and their toxicity to the predator Coccinella scpecnzpuncwla L. during the period from November 2004 to February 2005 at the Sher-e-l3angla Agricuhural University farm, Dhaka. The experimeni 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 control of mustard aphid and toxic effect to the predator under the different treatments were made at 1,4 and 7 days after first and second spraying of insecticides. Data on seed yield and yield parameters were taken at maturity. The percent reduction of aphid infested plant, percent reduction of aphid population and percent reduction of the predator varied significantly. Most of the crop characters and seed yield were significantly different due to usage of insecticides. Larva of C. sepiempuzciata consumed on an average 224.60 aphids during its 10 days of larval period and adult beetle consumed on an average of 885.40 aphids during 30 days period after emergence. The mortality of aphid, larvae and adult of the predator were significantly different. 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 to the predator. Cypermethrin showed higher effectiveness than other three insecticides in increasing growth parameters and seed yield of mustard. Considering benefit cost ratio (BCR). Cypermethrin was found most economic and effective insecticide in controlling L. wjsitni. The overall effectiveness of Cypenncthrin on mustard aphid and predator were found to be the best.