Effect of Different Insecticides against Insect Pests and Predators Complex on Brassica napus L., Under Field Conditions

The present study was conducted in the research area of Cotton Research Station, Multan during spring 2011. The main objective of the study was to evaluate the effect of different insecticides against mustard aphid (Lipaphis erysimi Kalt.), leaf miner (Phytomyza horticola Gour.), seven spotted lady beetle (Coccinella septumpunctata L.) and syrphid fly larvae under field conditions. Bifenthrin, diafentheuron, dimethoate and imidacloprid were the insecticides used and data was recorded before 1 day and after 1, 2, 3 and 7 days of spray application. Results on percent reduction indicated that bifenthrinwas most effective insecticide against L. erysimi and P. horticola. Bifenthrin caused 74.06% and 75.22% reduction in L. erysimi population and 85.13% and 84.02% reduction in P. horticola population after three and seven days of spraying. All insecticides were found toxic to the C. septumpunctata and syrphid fly larvae. However, Imidacloprid and dimethoate were found relatively safe as compared to other insecticides. Imidacloprid showed 57.34% reduction in C. septumpunctata population whereas dimethoate 52.77% reduction in larval population of syrphid flies after seven days of spray application. It is concluded that bifenthrin and imidacloprid can be used for the management of mustard insect pests because of their higher efficacy against aphids and leaf miners and less toxicity to beneficial insects.