Effects of Azadirachtin, Cypermethrin, Methoxyfenozide and Pyridalil on Functional Response of Habrobracon Hebetor Say (HYM.: Braconidae)

Habrobracon hebetor Say is one of the most important natural enemies of the Helicoverpa armigera Hübner (Lep.: Noctuidae). In this study, the sublethal effects of LC30 concentration of azadirachtin, cypermethrin, methoxyfenozide and pyridalil on the functional response of H. hebetor to different densities of 5th instars larvae of Ephestia kuehniella Zeller were evaluated. Young females were exposed to LC30 of the insecticides for an appropriate time of exposure. Then, six randomly selected alive females were transferred individually to plastic Petri dishes (10 cm in diameter) and supplied with the following densities: 2, 4, 8, 16, 32 and 64 of 5th instars of E. kuehniella for 24 h. Eight replicates were considered for each insecticide treatment and the control. The results revealed a type II functional response in the control, and all of the insecticide treatments. This study showed that the control and the cypermethrin treatment had the shortest (0.4143 h) and longest (0.624 h) handling time, respectively. The highest (0.0035 per hour) and lowest (0.0029 per hour) attack rate was observed in pyridalil and cypermethrin treatments, respectively. Based on values of handling time, cypermethrin had the highest adverse effect on host-finding in H. hebetor.