Monday, December 10, 2007 - 8:53 AM

How do predator foraging traits affect the predator-prey interaction and biological control of twospotted spider mites?

Punya Nachappa,, David C. Margolies,, and James R. Nechols, Kansas State University, Entomology, 124 Waters Hall, Manhattan, KS

An important factor for effective biological control using predators is the foraging efficiency, which is determined in part by the predatorís ability to locate and kill prey. Subtle behavioral changes related to prey consumption, the efficiency of converting prey into offspring and dispersal may lead to significant differences in predator-prey dynamics. We examined the effect of consumption, conversion efficiency and dispersal on the population dynamics of the twospotted spider mite and a predatory mite, Phytoseiulus persimilis Athias-Henriot. We used artificial selection to create lines of P. persimilis with high levels (relative to an unselected population) of the aforementioned traits. After selection, we assessed the impact of the foraging traits in time-replicated greenhouse experiments using blocks of 25 plants with patchy prey distribution. Predator lines were released at predator: prey ratio of either 1:10 (known to provide good suppression) or 1:30 (marginal suppression). We measured the number of prey, predators and plant damage per plant every 6 days up to 24 days. We also conducted a spatial analysis of predator-prey distribution. Initial results indicate that all selection lines were more effective in spider mite suppression and had less plant damage than the unselected population at either predator: prey ratio. The selection lines also produced greater number of predators than the unselected line. Spatial analysis indicated that reduction in spider mite population corresponded with the presence of the predatory mite. Results of our study will provide a critical link between predator foraging behaviors and population dynamics relevant to biological control.

Species 1: Acari Phytoseiidae Phytoseiulus persimilis (predatory mite)
Species 2: Acari Tetranychidae Tetranychus urticae (twospotted spider mite)