Control efficacy of fungus gnat, Bradysia impatiens, enhanced by a combination of entomopathogenic nematodes and predatory mites

Fungus gnat, Bradysia impatiens, is a serious soil pest of seedlings of various crops in the greenhouse and also in mushroom nurseries. Control with chemical pesticides may not be suitable because infestation mostly occurs indoors. Here, we determined the control efficacy of two biological agents: entomopathogenic nematodes (EPNs) and predatory mites, and investigated whether the combined treatments of these two agents improved the control efficacy of B. impatiens. Mortalities of various stages of B. impatiens maggots were determined in single treatments of two species of EPNs, Heterorhabditis indica and Steinernema carpocapsae, and two species of predatory mites, Androlaelaps casalis and Stratiolaelaps scimitus. EPNs were more effective in controlling the older larvae of B. impatiens and the effect was higher with H. indica than with S. carpocapsae. Predatory mites were more effective in controlling the younger larvae of B. impatiens and the effect was higher with S. scimitus than with A. casalis. Furthermore, the control efficacy was increased by the combination of EPNs and predatory mites, when compared with the single treatments. Particularly, the combination of H. indica and S. scimitus was higher than that of H. indica and A. casalis. Therefore, the combination of H. indica and S. scimitus can be used to improve the control efficacy of B. impatiens.