USE OF ENTOMOPATHOGENIC NEMATODES AND A NEW MONITORING TECHNIQUE FOR CONTROL OF FUNGUS GNATS, BRADYSIA-COPROPHILA (DIPTERA, SCIARIDAE), IN FLORICULTURE

Fungus gnats, Bradysia coprophila, damage plant roots and are involved in transmitting serious plant pathogens. The entomopathogenic nematod e Steinernema feltiae (SN) significantly reduced numbers of fungus gna t larvae in potting medium in greenhouse-grown poinsettias, Euphorbia pulcherrima, in comparison with Steinernema carpocapsae (All), the bac terial insecticide Bacillus thuringiensis subsp. israelensis, and the insect growth regulator kinoprene. Levels of insect control were indis tinguishable between Steinernema feltiae (SN) and the organophosphate insecticide diazinon, suggesting that the use of S. feltiae (SN) may b e both a biorational and an economical alternative to conventional che mical control. In a petri dish bioassay, second- and fourth-instar fun gus gnats were significantly more susceptible than pupae to infection by S. feltiae (SN). However, pupae mere susceptible to some level of n ematode infection not only by S. feltiae (SN), but also by S. feltiae (UK), S. carpocapsae (All), and Heterorhabditis bacteriophora (NC). Po tato discs placed on the potting medium proved to be a reliable method of monitoring fungus gnat populations in comparison to yellow sticky cards. (C) 1995 Academic Press, Inc.