TOXICITY EVALUATION OF PESTICIDES TO TETRANYCHUS URTICAE KOCH AND THEIR RESIDUAL EFFECTS ON COCCINELLA SEPTEMPUNCTATA L.

Abstract

The present study was carried out to determine the direct and residual effects of eight pesticides namely abamectin, abamectin+bifenthrin, spinosad, chlorfenapyr, deltamethrin, lambda-cyhalothrin, imidacloprid and thiamethoxam against Tetranychus urticae Koch (Acari: Tetranychidae) and residual toxicity of these pesticides against the pest and its predator Coccinella septempunctata L. (Coleoptera: Coccinellidae) adults. The laboratory trials, abamectin caused 100% mortality of T. urticae within 3 hours, abamectin+bifenthrin within 6 hours and other pesticides within 48 hours except imidacloprid and thiamethoxam. The egg mortality for all pesticide treatments was significantly higher than the control. Abamectin+bifenthrin and chlorfenapyr caused 100% egg mortality followed by abamectin (95%), deltamethrin (82%), lambdacyhalothrin (79%). On the other hand, thiamethoxam, imidacloprid and spinosad showed 63, 65 and 71% egg mortality, respectively. In potted bean plants, abamectin, abamectin+bifenthrin and chlorfenapyr showed significant mortality over control up to 21 days and the rest of pesticides showed up to 14 days. Abamectin and chlorfenapyr showed higher residual efficacy against T. urticae but low efficacy against C. septempunctata. Neonicotinoid, imidacloprid had the longest residual effect on adults of C. septempunctata causing 20% mortality after 21 days; but lower toxicity against T. urticae. Abamectin+bifenthrin residues caused >20% mortality of C. septempunctata after 14 days of exposure. Therefore, abamectin and chlorfenapyr can be used for the management of T. urticae because of their higher toxicity against T. urticae and less residual activity to C. septempunctata.