author(s)
Hajar Pakyari, Fazel Kasirloo, Abas Arbab

abstract
The sublethal affects of abamectin and fenpropathrin on the functional response of predatory coccinellid, Cryptolaemus montrouzieri Mulsant a potential biological control agent, were investigated on 4th-instar nymphs of Planococcus citri Risso as prey. The experiment was conducted in varying densities (2, 4, 8, 16, 32, 64 and 128) of P. citri at 28 ± 1 °C, 60%±10% relative humidity (RH) and a photoperiod of 16:8 h (L: D). The results of logistic regressions showed a type II functional response in the control and all insecticide concentrations. Comparison of functional response curves revealed that tested insecticides markedly decreased the mean of preys consumed by C. montrouzieri. The search rates found for predators decreased when exposed to increasing sublethal concentrations from LC₁₀ to LC₃₀ of both insecticides. The handling times of females exposed to insecticides were in all cases lower than in the control treatment. The maximum handling time observed in LC₁₀ of fenpropathrin and the minimum attack rate observed in LC₃₀ of abamectin. The maximum theoretical predation was increased when exposed to increasing sublethal concentrations from LC₁₀ to LC₃₀ of Abamectin but the highest theoretical maximum predation observed in LC₂₀ of fenpropathrin. The studies suggested that the adverse effect of these insecticides on C. montrouzieri must be considered in integrated pest management programs (IPM).