Functional response and mutual interference ofNeoseiulus californicusandTyphlodromus bagdasarjani(Acari: Phytoseiidae) onTetranychus urticae(Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most economically important pests on a wide range of crops over the world. This study was carried out to evaluate the efficacies of two predatory mite species, Neoseiulus californicus (McGregor), an introduced species in Iran, and Typhlodromus bagdasarjani Wainstein & Arutunjan, a native species, as biocontrol agents of Te. urticae. The functional response and mutual interference of these two phytoseiid mites were determined under laboratory conditions at 25°C, 65% RH and a photoperiod of 16 h light:8 h dark. The functional response of the two predator species to eggs or nymphs of Te. urticae was type II. The highest attack rate (0.0936 h–1) and the lowest handling time (1.6451 h) were recorded for N. californicus on eggs and the lowest attack rate (0.0473 h–1) and the highest handling time (2.399 h) were estimated for T. bagdasarjani on nymphs of Te. urticae. Nicholson's model and linear regression were used to determine the per capita searching efficiency and interference coefficient, respectively. The per capita searching efficiencies of the two predators decreased significantly with increasing predator densities. The interference coefficient for N. californicus was less than that for T. bagdasarjani. In addition, N. californicus had the highest predation potential, particularly on eggs of Te. urticae. Therefore, based on the attack rate and the handling time, N. californicus may be a more efficient biocontrol agent of Te. urticae on cucumber leaves in comparison to T. bagdasarjani.