EFFECTS OF ENTOMOPATHOGENIC NEMATODES ON CONTROL OF A MUSHROOM-INFESTING SCIARID FLY AND ON MUSHROOM PRODUCTION

The entomopathogenic nematodes Steinernema feltiae (Biosys strain #27) and Heterorhabditis heliothidis were evaluated for the larval control of a mushroom-infesting sciarid, Lycoriella mail, and for the effects of these nematodes on mushroom (Agaricus bisporus) production. In a s eries of small-scale mushroom crops, infective-stage H. heliothidis an d S. feltiae were applied to the mushroom casing surface in the irriga tion water or incorporated into the casing material at densities rangi ng from 28 to 1120 and II to 1120 nematodes cm(-2) of casing surface r espectively. The mortality of L. mail larvae ranged from 52 to 100% fo r H. heliothidis and 38 to 100% for S, feltiae. Both nematode species reduced mycelial coverage on the casing surface at primordia initiatio n. Neither mushroom strain (off-white or white hybrid) or method of ap plication (incorporation into or irrigation onto the casing surface) a ltered the effect on mycelial coverage. The nematodes's negative effec t on mycelial growth confounded the benefit of fly control. At high ne matode densities (lip to 1120 nematodes cm(-2)), damage-free mushroom yields for the first week of harvest were less than those from the unt reated control. However, at lower nematode densities, at or below 140 cm(-2), the nematodes had less effect on mushroom growth, and conseque ntly, damage-free mushroom yields for the first week of harvest- were frequently greater than those from the untreated control. In the absen ce of flies, the first-week mushroom yield generally declined with inc reasing nematode densities for both white and off-white mushroom hybri ds. After 4 weeks of harvest, accumulated mushroom yields had nearly r ecovered from the earlier decline.