The Association Between Mushroom Sciarid Flies, Cultural Techniques, and Green Mold Disease Incidence on Commercial Mushroom Farms

Compost Filling Methods Affect Green Mold Disease Incidence in Commercial Mushrooms

Green mold (Trichoderma aggressivum) is an invasive disease of commercial mushrooms introduced into the United States from Europe that now has spread to commercial mushrooms throughout North America. We examined potential sources of invasive green mold inoculum and the association with different compost filling technologies on a large actively producing commercial mushroom farm. Green mold foci were sampled bed by bed, which generated 20,906 data points. Logistic regression was used to determine treatment differences. Mechanical filling of compost into the beds reduced green mold incidence over hand filling, apparently due to the reduced incidence of worker contact with the floor and between beds. Lower growing beds located closer to the floor had a higher incidence of green mold for both mechanical and hand-filled beds. We conclude that mechanical filling and generally reducing contact with the floor and between beds will reduce spread of green mold in commercial mushroom production.

Regulation of Intracellular Reactive Oxygen Species Levels after the Development of Phallus rubrovolvatus Rot Disease Due to Trichoderma koningii Mycoparasitism

Phallus rubrovolvatus is a unique mushroom used for medicinal and dietary purposes in China. In recent years, however, the rot disease of P. rubrovolvatus has seriously affected its yield and quality, becoming an economically important threat. In this study, samples of symptomatic tissues were collected, isolated, and identified from five major P. rubrovolvatus production regions in Guizhou Province, China. Based on combined analyses of phylogenies (ITS and EF1-α), morphological characteristics and Koch's postulates, Trichoderma koningiopsis and Trichoderma koningii were identified as the pathogenic fungal species. Among these, T. koningii exhibited stronger pathogenicity than the other strains; thus, T. koningii was used as the test strain in the follow-up experiments. Upon co-culturing T. koningii with P. rubrovolvatus, the hyphae of the two species were intertwined, and the color of the P. rubrovolvatus hyphae changed from white to red. Moreover, T. koningii hyphae were wrapped around P. rubrovolvatus hyphae, leading to their shortening and convolution and ultimately inhibiting their growth due to wrinkling; T. koningii penetrated the entire basidiocarp tissue of P. rubrovolvatus, causing serious damage to the host basidiocarp cells. Further analyses revealed that T. koningii infection resulted in the swelling of basidiocarps and significantly enhanced the activity of defense-related enzymes, such as malondialdehyde, manganese peroxidase, and polyphenol oxidase. These findings offer theoretical support for further research on the infection mechanisms of pathogenic fungi and the prevention of diseases caused by them.

Microbial Control Agents for Fungus Gnats (Diptera: Sciaridae: Lycoriella) Affecting the Production of Oyster Mushrooms, Pleurotus spp

Infestations of fungus gnats (Diptera: Sciaridae) can reduce the production of oyster mushrooms (Pleurotus spp.) grown as food crops within controlled environments. The objectives of this study were to assess the efficacy of Bacillus thuringiensis var. israelensis (Bti) and Steinernema feltiae against fungus gnat larvae. A bioassay was developed, whereby pasteurized straw was inoculated with Pleurotus columbinus and treated with Bti (Gnatrol®), S. feltiae (Nemashield®), or water. Fungus gnats (Lycoriella sp.) were released into each bioassay container for ovipositing onto the straw, thereby exposing the F1 larvae to treated or untreated substrate. Sticky cards within the containers entrapped fungus gnats emerging from the substrate as an indicator of larval survivorship. Following three bioassays, fewer fungus gnats emerged from straw treated with Bti compared to S. feltiae and the water control. Three additional bioassays using Pleurotus ostreatus also demonstrated that fewer fungus gnats emerged from straw treated with Bti compared to S. feltiae and the untreated control. Steinernema feltiae was generally ineffective. Monitoring substrate weight in the bioassay containers over time indicated that Bti and S. feltiae did not impede colonization by P. ostreatus. Incorporating Bti into straw substrate is a promising approach for managing fungus gnats infesting Pleurotus spp.