Functional and numerical responses, mutual interference, and resource switching of Amblyseius swirskii on two-spotted spider mite

Abstract

The predatory mite Amblyseius swirskii Athias-Henriot (Acari, Mesostigmata: Phytoseiidae) has been used to control greenhouse pests including thrips, whiteflies and the two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari, Trombidiformes: Tetranychidae). This study evaluated A. swirskii’s potential to control TSSM by determining the functional response, numerical response, mutual interference, and prey switching behavior of the predator in the presence or absence of pollen under laboratory conditions. Type II and III functional responses were determined for A. swirskii fed on TSSM in the absence or presence of pollen, respectively. The highest predation rate and searching efficiency (a) was observed on eggs of TSSM compared with nymphs in all experiments. The numerical response of the predator showed a rapid and significant increase in oviposition with increasing TSSM density (both eggs and nymphs) but the rate gradually declined at higher densities of TSSM in both the presence and absence of pollen. The efficiency of conversion of ingested food (ECI) was highest at low prey density, and decreased at higher prey densities. The per capita searching efficiency of the predator also decreased significantly with increasing predator density. The interference coefficient for A. swirskii in the presence of pollen was less than that in the absence of pollen. Switching behavior was observed in A. swirskii in which the predator switched from one life stage of TSSM when it became rare to another, more abundant stage. The results of this study revealed high performance of A. swirskii on TSSM and the importance of pollen in its efficiency.