Effect of Sublethal Concentration of Buprofezin and Imidacloprid on Functional Response of the Parasitoid Wasp Encarsia inaron (Walker) (Hymenoptera: Aphelinidae)

Laboratory trials were conducted to measure the effects of two insecticides, imidacloprid and buprofezin on the functional response of Encarsia inaron (Walker) parasitizing Bemisia tabaci (Gennadius). Young female parasitoids (< 24h old) were exposed individually to LC25 valueof imidacloprid, field recommended concentration of buprofezin and distilled water as the control. Host densities of 2, 4, 8, 16, 32, and 64 third nymphal stages of B. tabaci were offered to treated females wasps for 24 h in clip cages on cucumber leaves. Experiments were conducted in 10 replicates and were carried out in controlled conditions, 25 ± 1oC, 70 ± 5%RH, and a photoperiod of 14: 10 (L: D). The type of functional response was determined using logistic regression and the parameters, searching efficiency (a) and handling time (Th) were estimated by the non-linear regression using SAS software. The functional response was type II in the control and both insecticide treatments. Searching efficiency in the control, buprofezin and imidacloprid were 0.0413, 0.0360 and 0.0373 h-1 and the handling times were 2.9727, 1.2738 and 2.0187 h, respectively. The maximum attack rates (T/ Th) were estimated 8.07, 18.84 and 11.89, respectively. Neither of insecticides had detrimental effect on the searching efficacy of E. inaron.