Evaluation of the predatory mite Phytoseiulus macropilis (Acari: Phytoseiidae) as a biological control agent of the two-spotted spider mite on strawberry plants under greenhouse conditions.

The predatory mite Phytoseiulus macropilis is a potential biological control agent of the two-spotted spider mite (TSSM) Tetranychus urticae on strawberry plants. Its ability to control TSSM was recently assessed under laboratory conditions, but its ability to locate and control TSSM under greenhouse conditions has not been tested so far. We evaluated whether P. macropilis is able to control TSSM on strawberry plants and to locate strawberry plants infested with TSSM under greenhouse conditions. Additionally, we tested, in an olfactometer, whether odours play a role in prey-finding by P. macropilis. The predatory mite P. macropilis required about 20 days to achieve reduction of the TSSM population on strawberry plants initially infested with 100 TSSM females per plant. TSSM-infested plants attract an average of 27.5 +/- 1.0% of the predators recaptured per plant and uninfested plants attracted only 5.8 +/- 1.0% per plant. The predatory mites were able to suppress TSSM populations on a single strawberry plant and were able to use odours from TSSM-infested strawberry plants to locate prey in both olfactometer and arena experiments. Hence, it is concluded that P. macropilis can locate and reduce TSSM population on strawberry plants under greenhouse conditions.