Plant architecture, prey distribution and predator release strategy interact to affect foraging efficiency of the predatory mite Phytoseiulus persimilis (Acari: Phytoseiidae) on cucumber

Abstract

We examined the ability of adult predatory mites, Phytoseiulus persimilis Athias-Henriot, to search for and consume twospotted spider mites, Tetranychus urticae Koch, on cucumber plants that were manipulated to exhibit different architectures and prey distributions among leaves. Plants were manipulated to have either six small leaves or two large leaves; however, both plants types had similar total surface areas. Prey were located either all on one basal leaf or evenly distributed among all leaves. In one experiment, we measured prey-finding time when predators were released at the top or bottom of plants. Regardless of release point, P. persimilis found prey more rapidly when prey were on all leaves. On such plants, P. persimilis found prey patches first on leaves closest to the release point. Predator release point only affected prey-finding time when prey were located on the basal leaf of 6-leafed plants; it was longer when predators were released at the top. In a second experiment, we measured consumption and oviposition rates of predatory mites. Phytoseiulus persimilis consumed more prey on six-leafed than two-leaved plants regardless of prey distribution. Prey consumption and predator oviposition was highest on prey patches nearest the release point. We conclude that releasing P. persimilis over the plant canopy may not be effective during early stages of spider mite infestations on plants with a complex architecture. Both prey distribution and plant architecture should be considered when making decisions concerning release of P. persimilis in augmentative biological control programs.