Abstract
Coccinella septempunctata L. is a dominant predator of herbivorous pest insects (e.g. aphids) in various crops in Pakistan. A series of bioassays were conducted to determine the sublethal and residual activities of six insecticides, which are commonly used in canola crop (Brassica napus L.) in Pakistan on adult and fourth instar larvae of Coccinella septempunctata L. in laboratory conditions. We measured the mortality, uncoordination and consumption rate of coccinellid beetle to identify the products with comparatively low toxicity or short duration effects. Six insecticides (imidacloprid, thiamethoxam, profenophos, chlorpyriphos, lambda-cyhalothrin and cypermethrin) were used to treat aphids and arenas at sublethal concentration (LC30). Compared to control treatment, increased mortality and knockdown effects were observed following contact with residues and prey treated with all insecticides. While predatory efficiency of both adult and larval stages of C. septempunctata was significantly decreased after treatments. However, significantly lower mortality and high prey consumption were observed after treatment with imidacloprid and thiamethoxam (neonicotinoids) compared to other four insecticides. Results of choice and no-choice tests using field doses and 1/2 field doses also confirmed the significant difference in consumption of prey between imidacloprid, thiamethoxam and other four chemicals. Larvae and adult of C. septempunctata preferentially consumed untreated aphids than treated aphids with 1/2 and maximum field dose over the 5h experimental period. This study provides information to guide canola growers in their selection of insecticides.