Biological control of the fungus gnats Bradysia difformis (Diptera, Mycetophilidae) in mushrooms with Heterorhabditis amazonensis in tropical conditions

Abstract

Sciarids from the genus Bradysia have gained attention due to their damaging presence in many protected crops in both temperate and tropical environments. In Venezuela, these flies called “fungus gnat” have turned into a hard pest to control in mushroom facilities, due to restrictions on the usage of chemical product after setting the casing layer and during the fructification period. For these reasons, we evaluated the use of native entomopathogenic nematodes as biological control agents to control Bradysia difformis in both laboratory and field conditions. Different Venezuelan nematode species or isolates were tested using fungus gnat larvae in laboratory condition, of which Heterorhabditis amazonensis (LPV-498) was the best performer at low temperatures. The nematodes were then tested in commercial mushroom farms using different dosses and application times. In the present work, H. amazonensis demonstrated that bags treated with nematodes, produced more mushrooms per bag than those treated with the normal chemical protocols. The highest production was reached when 3 million nematodes were applied after setting the casing layer, with 3766±1004g of harvested mushrooms per bag, an 44% increase of mushroom yield of compared with bags treated only with chemical products.