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.
Description:
A Thesis
Submitted to the Faculty of Agriculture,
Sher-e-Bangla Agricultural University, Dhaka,
in partial fulJIllinent of the requirements for the degree of
MASTER OF SCIENCE IN ENTOMOLOGY
SEMESTER: JULY-DECEMBER, 2006