Comparing mushroom fly responses to spawned compost volatiles of different ages

Mushroom flies (Megaselia halterata) are a major pest of commercially grown mushrooms worldwide requiring novel and effective control methods to protect mushroom production. Female mushroom flies lay their eggs within spawned compost on mushroom farms. Their larvae feed on growing mycelium, reducing mushroom yield and quality. Female flies lay eggs on compost during early mycelium growth 4 to 10 days after spawning. We hypothesize that female mushroom flies select rooms containing spawned compost in the 4-10 day range based on volatile organic compounds. In this study, we sampled mushroom compost volatiles every 3-4 days from day 0 to day 48, or the beginning of the spawn run to the end of mushroom growing cycle. GC-MS analysis compared differences in volatile extracts throughout the growing cycle to find changes in the identity and quantity of specific volatiles. We then exposed female flies to volatile extracts using GC-EAD and behavioral bioassays. Female behavioral responses to different ages of compost, and the chemical extracts from that compost were observed to characterize behaviors driven by these odorants. A strong behavioral attraction to the volatiles can be developed into traps or attract and kill stations for flies, and repellent volatile extracts could deter flies from egg-laying in freshly spawned mushroom farms. We can develop better, more sustainable methods of managing pest populations worldwide by controlling the volatile behavior of these flies using their natural responses to these volatiles.