Dalotia coriaria Kraatz (Coleoptera: Staphylinidae) is a commercially available, soil-dwelling predator that preys upon a variety of insect pests that reside in soils or growing media. The impact of D. coriaria on the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), however, is not well documented. Three laboratory experiments were conducted to assess predation efficacy of D. coriaria adults on western flower thrips pupal populations typically found in the soil or growing medium. Treatments included prepupae only, pupae only, and a prepupae-pupae combination (1:1). Six numbers (0, 1, 2, 3, 4, and 5) of beetle adults and four initial numbers (15, 20, 25, and 30) of thrips pupal populations were examined for each pupal stage treatment. For each pupal stage treatment, the estimated mean probability of thrips adults captured on yellow sticky cards decreased as the number of beetle adults released increased from one to three, but there was no significant effect after releasing additional beetles. Furthermore, there were no differences in response to the predator:prey ratio or initial prey number within each predator:prey ratio examined across the pupal populations examined in this study. These results (a) provide insight into the predatory behavior of D. coriaria adults on western flower thrips pupal populations, which may have practical implications for greenhouse production systems; and (b) indicate that, regardless of the initial numbers of western flower thrips prepupae and/or pupae in the growing medium, three D. coriaria adults per 15.2-cm container may be recommended for use of this predator against western flower thrips.

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