Parasitoid wasps regulate population growth of fungus gnats genus Neoempheria Osten Sacken (Diptera: Mycetophilidae) in shiitake mushroom cultivation

Abstract

The fungus gnats genus Neoempheria Osten Sacken (Diptera: Mycetophilidae) are pests of the edible shiitake mushroom, Lentinula edodes (Berk.) Sing. (Agaricales: Omphalotaceae). In mushroom cultivation, there is a need to establish sustainable approaches with low environmental impact for insect pest control. Such practices should integrate cultural, chemical, and biological strategies. We investigated the ability of hymenopteran parasitoids to control population growth of fungus gnats during the growing of shiitake mushrooms. We found that females of two species of Orthocentrinae (Hymenoptera: Ichneumonidae), Orthocentrus sp. and Symplecis bicingulata Gravenhorst, attack larvae of the fungus gnat, Neoempheria spp. We investigated the temporal population changes of fungus gnats and its parasitoids. We counted the numbers of adult Neoempheria spp. and parasitoids by using adhesive sheet traps. We also counted the number of larval Neoempheria spp. on each mycelial culture block, and we collected some of the larvae to investigate parasitism rates within each cultivation facility. Generally, the numbers of adult Neoempheria spp. increased gradually from early cultivation onward. Parasitoid numbers and parasitism rates increased toward the end of cultivation, as fungus gnat larvae populations decreased. Additionally, after the release of Neoempheria spp. larvae with Orthocentrus sp. in the treatment plots of shiitake mushroom cultivation greenhouse, the next generation of Neoempheria spp. was significantly less populous in plots containing parasitoids than in control plots without parasitoids. The parasitoid may be an important natural enemy of fungus gnats in shiitake mushroom-growing ecosystems and possesses great potential for use in biological control.