Foraging efficiency of selected lines of the predatory mite, (Phytoseiulus persimilis) with different prey distributions on cucumber plants

Abstract. Many crops grown in greenhouses are damaged by twospotted spider mites, Tetranychus urticae. The predatory mite, Phytoseiulus persimilis, is a commercially-available predator that is commonly used to control twospotted spider mites, but its efficacy varies among crops and is generally low at low prey densities. Predator foraging efficiency depends on how well predators find prey patches, the length of stay in prey patches, and consumption of spider mites while in prey patches. We asked how predators respond to different distributions and densities of prey, such as they might encounter at different stages of spider mite infestations. We also asked how components of foraging, namely consumption rate and dispersal tendency, affected predator efficiency. To examine the former we established spider mites on 6-leafed cucumber plants in two distributions and densities. To examine the later imposed artificial selection on a population of P. persimilis to create a line with extremely high consumption and a line with extremely high dispersal. Foraging efficiency was assessed by observing predator oviposition and consumption of twospotted mite eggs. Spider mite distribution and density did not affect either predator consumption or oviposition. Predator foraging attributes did not affect oviposition, but the high dispersal line ate significantly fewer prey (9.07 ± 3.3) than did the high consumption line (22.2 ± 3.5) or unselected control (20.1 ± 3.0). We expect such results will aid in IPM and biological control strategies in complex landscapes.