Abstract: Leaf disc bioassay was employed in the laboratory to investigate the effects of selected pesticides, including abamectin and chlorpyrifos, on the functional response of an acarophagous thrips, Scolothrips takahashii Prisener to a damaging spider mite, Tetranychus viennensis Zacher eggs under the conditions of 25℃±1℃, RH 60%±10%, and a photoperiod of 16L∶8D. Two doses, viz. the labeled dose and half of the labeled dose, of the selected pesticides were tested. Logistic regression was used to determine the type of functional response and to compare predation performance at various prey densities; parameters of random predator equation for both exposed and unexposed predators were estimated and then compared with an equation with indicator variables. The results showed that the two insecticides exerted profound influence on the functional response of the acarophagous thrips. Exposed to labeled dose of abamectin, both males and females thrips exhibited significant lower attack rates, markedly extended handling time was also recorded, and functional response for females in the labeled dose exposure was confirmed to be Holling-Ⅲ type, rather than Holling-Ⅱ type in the control. An exposure of half labeled dose of abamectin had no obvious influence on the attack rates of both sexes of the predator, but handling time in females prolonged significantly. Exposures of the two doses of chloryprifos resulted in attack rates reduced notably in both male and female thrips, with the handling time extended by 85.62% and 71.97% in the female and 55.92% and 38.20% in the male respectively, and functional responses for both males and females were proved to be Holling-Ⅱ type, same as those in the control.

Key words: Scolothrips takahashii, Tetranychus viennensis, functional response, abamectin, chlorpyrifos