Olfactory responses of the predatory mite Amblyseius andersoni Chant (Acari, Phytoseiidae) to bean plants infested by the spider mite Tetranychus urticae Koch (Acari, Tetranychidae)

The responses of the predatory mite Amblyseius andersoni Chant adult females to odours emanating from whole bean plants or excised leaves infested by adult females of Tetranychus urticae Koch, or to possible odours from females of T. urticae were studied in the laboratory using a Y-tube olfactometer. A. andersoni females exhibited a stronger positive response to odours from infested plants or leaves than to the uninfested ones. This preference was maintained even after the colonies of the spider mite were removed from the surface of the infested leaves and the leaves were rinsed with water. However, A. andersoni females did not show a preference for possible odours released by adult females of T. urticae or pin-pricked uninfested leaves. These results suggest that the factor(s) motivating the selection of infested plants by the predator is probably associated with the previous infestation of the plants by the spider mite.