Use of Entomopathogenic Nematodes and a New Monitoring Technique for Control of Fungus Gnats, Bradysia coprophila (Diptera: Sciaridae), in Floriculture

Abstract

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