Toxicity of pesticides toTetranychus urticaeKoch (Acari:Tetranychidae) and their side effects onNeoseiulus californicus(Acari:Phytoseiidae)

The present study was conducted to determine the direct and residual effects of five pesticides, namely abamectin, bifenthrin, dimethoate, propargite and sulphur against Tetranychus urticae and residual toxicity of these pesticides to Neoseiulus californicus adults. In the laboratory trials, except dimethoate, all the pesticide treatments caused 100% mortality of T. urticae adults within 24–48 hours. When toxicity to eggs was tested, the egg mortality for all pesticide treatments was significantly higher than the control. Except dimethoate, all the pesticides caused >90% egg mortality. In potted bean plants, all the pesticide treatments caused significant mortality of T. urticae populations over control up to 21 days. The residual effects of pesticides were tested on T. urticae and N. californicus using a leaf disc system in the laboratory. Mites were exposed to freshly sprayed leaf disc and after at 3, 7, 14 and 21. Abamectin showed higher efficacy against T. urticae but low toxicity against N. californicus. Residual toxicity of pesticides to N. californicus adults varied but remained toxic to N. californicus longer than to T. urticae. Bifenthrin had the longest residual effect on adults N. californicus, causing mortality of 23% after 21 days; propargite and dimethoate caused <30% mortality after 14 days of exposure.