Response of the functional of Hippodamia variegate preying on pea aphid Acyrthosiphon pisum to sublethal doses of 3 insecticides

This study was conducted to investigate the effects of sublethal doses of insecticides on functional response of Hippodamia variegate preying on Acyrthosiphon pisum, and thus provide some useful theoretical references for the effective coordination of chemical and biological control. We utilized sublethal doses of 3 insecticides, imidacloprid, abamectin and alphacypermethrin, and studied the changes of predatory capacities, functional response predator-prey model, predatory rates and searching efficiency on H. variegate by the two models of stomach poisoning and contacting toxicity. The results showed that among sublethal doses of 3 insecticides, the effect of beta-cypermethrin on H. variegate was the maximum, while imidacloprid was the minimum. In sublethal doses of pesticides, the functional response models of H. variegate preying on A. pisum were still conformed to Holling’s type Ⅱ curve in spite of pretreated with sublethal doses of insecticide; while the parameters of models had some changes. The discovery rates decreased by 6.01%~25.81%; the handling time prolonged by 17.32%~71.82%; and the maximal predatory capacities reduced by 14.75%~41.80%. Besides, the predatory capacities, predatory rates and searching efficiency decreased by 6.71%~37.36%, 9.81%~29.45% and 29.58%~7.85%, respectively. These findings suggested that 3 insecticides at sublethal level had some inhibition influence on the predation of H. variegate.