Comparative toxicity of botanical and reduced-risk insecticides to Mediterranean populations of Tetranychus urticae and Phytoseiulus persimilis (Acari Tetranychidae, Phytoseiidae)

The two-spotted spider mite Tetranychus urticae and its predator Phytoseiulus persimilis are widely spread throughout the Mediterranean area. Predator-prey interactions in crops may be affected by pesticides used to control other pests, and thus knowledge of pesticide side-effects is essential when managing spider mite populations following integrated pest management (IPM). Toxicological studies evaluating the effects of pesticides on both predator and prey can better predict their impact on mite communities. The botanical and reduced-risk insecticides recommended for the control of aphids, whiteflies and thrips, Biopiren((R)) plus (pyrethrins), Confidor((R)) (imidacloprid), Naturalis((R)) (Beauveria bassiano), Oikos((R)) (azadirachtin), Plenum((R)) (pymetrozine) and Rotena((R)) (rotenone) were evaluated on T. urticae and P. persimilis females in the laboratory. Mite populations were collected on unsprayed vegetables in the Mediterranean area (island of Sardinia). Mite females were treated by micro-immersion and then reared on treated leaves in holding cells. The survival, fecundity and fertility of mites were assessed. All the products affected mite survival and/or fecundity. Pyrethrins and rotenone were more toxic to P. persimilis than to T. urticae; azadirachtin, B. bassiana and pymetrozine showed an opposite tendency. Imidacloprid had a similar impact on predator and prey. Additional toxicological trials were conducted with T. urticae and P. persimilis eggs. Beauveria bassiana was the most effective pesticide in reducing the hatching of T. urticae treated eggs and rotenone significantly affected P. persimilis egg hatching. (C) 2008 Elsevier Inc. All rights reserved.