The invasive tomato spider mite, Tetranychus evansi (Acari: Tetranychidae) is one of the major pests of the solanaceous plants worldwide. The phytoseiid predatory mite Amblyseius swirskii (Acari: Phytoseiidae) is one of the most commonly used predatory mites for augmentative biological control of several important pests in protected crops. Despite its frequent usage in a range of greenhouse crops including tomatoes, several biological characteristics and foraging behaviors of this predator such as functional and numerical responses, have not been studied on T. evansi. In this study, the functional and numerical responses of A. swirskii to four different biological stages (eggs, larvae, protonymphs and deutonymphs) of T. evansi were evaluated under laboratory conditions. The significantly negative P1 values and the type of functional response curves clearly indicate that A. swirskii exhibited a Type II functional response to T. evansi regardless of prey stage. The highest attack rate (α=0.070 h-1) and the shortest handling time (Th=0.426 h) were determined when the predator fed on protonymph and larva, respectively. The highest daily mean number of eggs (1.10±0.10) laid by A. swirskii was obtained at 120 egg density. No significant difference was determined in egg production of the predatory mite among different life stages within the same prey density except 10 prey density. In addition, there was also no difference among prey densities within the same biological stage, except egg stage. According to the results, A. swirskii may not be directly recommended for the biological control of T. evansi on tomato. However, when its inundative release is considered, it may help and improve the success of biological control of T. evansi, especially at early stages of infestations.
tomato spider mite