D3198: Biological control of the mushroom phorid fly with predatory mites in laboratory bioassays

The mushroom phorid fly, Megaselia halterata, reduces mushroom quality and yields through feeding on the actively growing mycelium and via transmission of pathogenic green mold (Trichoderma agressivum). M. halterata infestations also plague local communities in the areas surrounding mushroom farms. Here we evaluate the potential for the predatory mite Stratiolaelaps scimitus to control M. halterata populations in laboratory bioassays. We examine the effect of dosage and application timing on efficacy, quantified as fly mortality compared to the negative control. We also sampled the medium containing the mites to assess the population dynamics of both S. scimitus and the mold mite Tyrophagus putrescientiae, which is included as a food source for the predatory mites. All four treatments of predatory mites resulted in significant reductions compared to the negative control. The treatment with the highest dosage and the earliest application had the highest relative fly mortality (63.5%). The treatment with the highest dosage and latest application had the second highest relative mortality (61.6%). Results from population dynamics tests will also be presented. Preliminary results suggest T. putrescientiae decreases over a two-week period, while populations of the predatory mite S. scimitus remain stable over the same time frame. The results from this experiment will be used to design IPM strategies incorporating S. scimitus to control M. halterata on mushroom farms.