Effect of Bacillus thuringiensis subsp. israelensis and neonicotinoid insecticides on the fungus gnat Bradysia sp nr. coprophila (Lintner) (Diptera: Sciaridae).

The soil bacterium Bacillus thuringiensis Berliner subsp. israelensis (Bti), the neonicotinoid insecticides dinotefuran, imidacloprid, thiamethoxam and clothianidin and the insect growth regulator pyriproxyfen were evaluated to determine their efficacy against the larval stages of the fungus gnat Bradysia sp nr. coprophila (Lintner) in the laboratory. Treatments were applied as a drench to the growing medium in polypropylene deli containers. The Bti treatments had no effect on either instar tested, whereas all the other compounds negatively affected both the second and third instars. This study demonstrates that the soil bacterium B. thuringiensis var. israelensis may not be active on these larval stages, whereas the neonicotinoid insecticides and the insect growth regulator pyriproxyfen are effective on these stages. The fact that Bti is not effective on the second and third instars of the fungus gnat means that greenhouse producers using this insecticide must make applications before fungus gnat populations build up and before overlapping generations develop.