D3098: Assessing the efficacy of Steinernema carpocapsae for biological control of Megaselia halterata on mushroom farms

Mushroom flies, Megaselia halterata (mushroom phorid) and Lycoriella ingenua (fungus gnat), reduce the quality and yield of mushrooms through larval feeding, and by vectoring disease. Laboratory studies were developed to determine whether Steinernema carpocapsae could infect mushroom flies. Nematodes were applied at the max application rate to a petri dish filled with compost and 5 fly larvae (2^nd or 3^rd instars). Petri dishes were incubated (20.5 ˚C, 70% RH, 12:12 L:D). Larval mortality was monitored 48 hours post application. The average mortality of M. halterata was significantly higher (P < 0.05) in nematode treatments (60 % ± 0.25 S. E.), compared to that of water (32% ± 0.21 S. E.) and negative control treatments (14% ± 0.26 S.E.). Nematodes did not induce mortality in L. ingenua. To replicate farm conditions, 10 mating pairs of M. halterata adults (1 day post eclosion) were introduced into a colony rearing cup (16 oz cup containing compost). Two application times were tested to understand the impact of larval development on nematode infestation. Flies mated and laid eggs in cups, and either nematodes or water was applied after 7 or 14 days. Cups were incubated and emergence was counted for 52 days. Average emergence was 65% lower in nematode treatments compared to control treatments, suggesting S. carpocapsae may be a viable control strategy for M. halterata on farms. Data from field studies on commercial mushroom farms will be presented. Fly counts, as well as mushroom yield and quality will be used to assess IPM strategies.