SD77: Developing mite application protocols to control mushroom flies in controlled environments

The mushroom phorid fly, Megaselia halterata, reduces mushroom quality and yield by feeding on actively growing mycelium as larvae and via transmission of fungal pathogens that cause mushroom diseases as adults. The mushroom sciarid fly, Lycoriella ingenua, is a secondary pest that damages mushrooms similarly. With no proven larvicides and few available adulticides for M. halterata, demand has grown for effective larvicides to reduce fly populations. To meet this demand, we are assessing larvicidal predators to disrupt the life cycle of the flies and control populations on farms. We first demonstrated that the predatory mite, Stratiolaelaps scimitus, preyed on M. halterata larvae in laboratory studies. We also demonstrated that S. scimitus did not inhibit mushroom mycelial colonization or transmit the fungal pathogen that causes dry bubble disease in mushrooms in laboratory studies. These laboratory results justified field experiments assessing the effect of mite applications on M. halterata and L. ingenua populations in growing rooms throughout the mushroom growing cycle. Treatment rooms with mite applications were compared to rooms without any mites applied. 25,000 mites per 1,000 sq ft were applied to the compost in treatment rooms at the beginning of the growing cycle when gravid female flies begin laying eggs. Flies were counted on light traps weekly throughout the growing cycle to assess the ability of the mites to disrupt the life cycle of the flies. Data will be presented from these ongoing field studies.