Phorid flies are a vector of green mold (Trichoderma aggressivum), a major disease problem in the production of mushrooms. Notably, most materials used to control flies in mushroom production that are effective in controlling sciarid flies are not effective in controlling phorid flies. For these reasons, the Biopesticide and Organic Support Program funded research on phorid fly management in mushroom growing operations in 2017 and 2018. The protocol included PFR-97, Grandevo, and JMS Stylet-Oil. In both 2017 California experiments, there was on average a 70% reduction in total fly population in the treated rooms versus the un-treated control rooms. No yield reduction was observed in the treated rooms versus the control rooms. However, 2017 Pennsylvania experiments indicated that applications of PFR-97 and Grandevo at label recommended rates did not significantly reduce the number of phorid flies. The results for 2018 are still incoming. Hopefully, IR-4’s contributions will provide a solution to this pesky problem.