Laboratory evaluation of Orthocentrus brachycerus (Hymenoptera: Ichneumonidae), as a potential biological control agent in mushroom cultivation

Fungus gnats in the genus Neoempheria Osten Sacken (Diptera: Mycetophilidae) are serious pests of the shiitake mushroom, Lentinula edodes (Berk.) Sing. (Agaricales: Omphalotaceae), a prize edible. Recently, we found that the parasitoid wasp Orthocentrus brachycerus Humala & Lee, 2020 (Hymenoptera: Ichneumonidae) attacks larvae of Neoempheria. We have shown in previous research that O. brachycerus suppresses population growth of Neoempheria in simulated cultivation conditions, and thus shows potential for use as a biological control agent. However, the behavioural and ecological aspects of this wasp have not been studied. Here, under controlled laboratory conditions, we investigated the fecundity, longevity and host stage specificity of O. brachycerus against Neoempheria larvae. We found that O. brachycerus are prolific throughout their life cycle. On average, female O. brachycerus made over 140 attempts to parasitize pest larvae, and over 90% of Neoempheria larvae were parasitized or died before emergence. Parasitoid females kept at 20°C survived for an average of 15.4 ± 3.58 days, and some females survived >30 days. Females continued to oviposit eggs throughout their life cycle and parasitized all stages of host larvae, but not eggs. These observations indicate that O. brachycerus may be effective for control of Neoempheria larvae in shiitake cultivation facilities. These results provide a basis for establishing a protocol for using O. brachycerus in mushroom cultivation.