Effect of imidacloprid and pirimicarb on functional response of Aphidius matricariae Haliday (Hym: Braconidae) under laboratory conditions

Study of natural enemies responses to different densities of hosts, is one of the most important criteria that can be used to select a suitable natural enemy in biological control programs. On the other hand, application of insecticides to pest’s controls may affect the behavioral responses such as functional response as well as efficiency of natural enemy. In this research, effect of imidacloprid and pirimicarb was studied on functional response of Aphidius matricariae (Haliday) to densities of 2, 4, 8, 16, 32 and 64 of third instar nymphs of Aphis gossypii (Glover) under laboratory conditions (25±1 0C, 65±5% R.H. and 16:8 (L:D) h). Mated females (< 12 h old) were exposed to LC25 of mentioned insecticides and distilled water as control in glass tubes. Experiments were conducted in 10 replicates. Functional response type was determined using logistic regression and the parameters, were estimated by non-linear regression using SAS program. Functional response on control and insecticides treatments fitted the type II. Attack rate (a) in control and insecticides treatments were estimated 0.0645, 0.0373 and 0.0452 h-1 and handling time (Th) were 0.4607, 0.8873 and 0.6292 h, respectively. The maximum attach rate (T/Th) was calculated 52.09, 27.05 and 38.14, respectively. The results indicated that pirimicarb had the lowest effect on handling time of A. matricariae in comparison with imidacloprid.