Mushroom sciarid fly, Lycoriella ingenua (Diptera: Sciaridae) adults and larvae vector Mushroom Green Mold (Trichoderma aggressivum ft. aggressivum) spores

Abstract

Gravid female mushroom sciarid flies, Lycoriella ingenua (Dufour:1839) (Diptera:Sciaridae), were confirmed in laboratory experiments as vectors for the fungal pathogen Trichoderma aggressivum f. aggressivum (Samuels and Gams), causal agent of mushroom green mold disease in mushroom farming. The gravid females acquired the fungal spores when exposed to T. aggressivum cultures, which was confirmed by scanning electron microscopy, the flies vectored T. aggressivum onto clean agar petri dishes, confirmed by new fungal colonies growing on the media and molecular analysis (PCR). Significantly, more T. aggressivum colonies formed on the dishes when flies were left to vector the pathogen for 30 h, as opposed to 18 h. One gravid female fly was able to initiate up to 32 T. aggressivum colonies in a 0.03 m3 area. Frass deposits of mushroom sciarid fly larva reared on T. aggressivum contained viable spores, detected through fungal subcultures and molecular analysis (PCR), confirming that larvae can also vector the fungus. This study supports the heretofore anecdotal evidence that mushroom sciarid flies are part of green mold disease epidemiology on mushroom farms.