Evaluating the effectiveness of long-lasting insecticide nets for mushroom phorid fly management

The mushroom phorid fly, Megaselia halterata, is a significant pest of cultivated mushrooms, with its larvae feeding on mushroom mycelia and adults spreading diseases, thereby reducing yield. Conventional pesticide usage can harm mushroom mycelia, reducing yields and quality, and may leave residues on harvested mushrooms, highlighting the need for safer alternatives. Long-lasting insecticide nets (LLINs) have been reported to be used in the management of agricultural insect pests both in pre- and post-harvest systems. Previous studies testing the efficacy of different LLIN prototypes against M. halterata identified PermaNet® 3.0, containing deltamethrin and the synergist piperonyl butoxide, as the most promising, with >90% initial mortality and sustained >70% mortality over seven months. This current study examined the effectiveness of long-lasting insecticide nets (PermaNet® 3.0) for the management of M. halterata on mushroom farms. Adult flies were exposed to PermaNet 3.0 for varying durations to determine the duration required to acquire a lethal insecticidal dosage. We also examined the potential of PermaNet 3.0 in reducing adult and larval populations in mushroom farms. Results from the pilot trials indicated that wrapping compost with PermaNet 3.0 reduced mushroom phorid larval counts by 90%, and covering the doors, compost, and picking lights of compost incubation rooms decreased adult fly numbers by 62%. Additionally, a 100% mortality rate was recorded 9 hours post-exposure, irrespective of the exposure time. Results from this study will have implications for the development of integrated pest management strategies for M. halterata, with the potential to improve mushroom yield and quality.