EFFICIENCY AGAINST THE TWO-SPOTTED SPIDER MITE TETRANYCHUS URTICAE AND PREY-AGE-RELATED CHOICE OF THREE PREDATORY MITE

Specialist and generalist predator mites have been recommended against the two-spotted spider mite (Tetranycus urticae) as biological control agents, but their effectiveness in population regulation has been rarely examined under circumstances when prey had the opportunity to express antipredatory responses. We tested the efficiency and preference for prey life stages of three predator mites, one specialist (Phytoseiulus persimilis) and two generalists (Amblyseius swirskii and Iphiseius degenerans). We used two predator densities and performed the experiment under 'seminatural'conditions. We found that significantly less eggs and adult spider mites survived in the presence of P. persimilis compared to the control group, and this predator mite consumed more eggs at high density than the other predators. In the presence of A. swirskii fewer adult spider mites survived at low density compared to the control, whereas egg survival was lower than in the control group at both densities. In the presence of I. degenerans, only the survival of eggs was lower than in the control group and only at high density. Our results suggest that the generalist A. swirskii, but not I. degenerans, may be efficient in regulating prey populations through egg consumption, and, thus, represents an alternative to the effective specialist predator.