Compatibility of soil-dwelling predators and microbial agents and their efficacy in controlling soil-dwelling stages of western flower thrips Frankliniella occidentalis

Western flower thrips (WFT) generally pupate in the soil. This laboratory study was designed to examine the compatibility of soil-dwelling predators with microbial biocontrol agents and assess their combined efficacy against pupating WFT, with a view to their integrated use. The following commercially available biocontrol agents were evaluated: a rove beetle, Dalotia coriaria (Kraatz); predatory mites, Stratiolaelaps scimitus (Womersley) and Gaeolaelaps gillespiei Beaulieu; entomopathogenic fungi, Metarhizium anisopliae (Metschnikoff) Sorokin (now classified as Metarhizium brunneum) strain F52 and Beauveria bassiana (Balsamo) GHA strain; and the nematode, Steinernema feltiae (Filipjev). Compatibility studies demonstrated mortality caused by the microbial agents ranging from 2.93% to 60.95% against the predators tested. In container studies, efficacy against WFT was significantly improved when the predators and fungi were combined, achieving >90% thrips mortality, compared to the treatments in which they were used separately. This was not observed with nematodes.