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ARS Home » Research » Publications at this Location » Publication #79552
Title: FUNGAL-INDUCED COLLAPSE OF A LEADING EDGE GYPSY MOTH POPULATION IN SOUTHWESTERN VIRGINIA

Author
item WEBB, RALPH
item WHITE, GEOFFREY
item THORPE, KEVIN
item TALLEY, S - ROCKBRIDGE CO GYPSY MOTH

Submitted to: United States Department of Agricultural Interagency Gypsy Moth Research Forum
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: In 1995 and 1996, 10 woodlots were monitored for the presence of gypsy moth nuclear polyhedrosis virus (NPV) and the fungus Entomophaga maimaiga (fungus). Gypsy moth populations varied from very sparse to high (potentially defoliating levels). NPV was strongly density dependent, the fungus was equally active at all population levels. In 1995, perhaps due to 1) fewer inoculative resting spores from 1994, 2) weather events, and/or 3) earlier gypsy moth population development, the fungal epizootic developed late in the season, with most larvae succumbing during instars 5-6, producing primarily resting spores (azygospores). In 1996, perhaps due to 1) the large number of overwintering resting spores produced in 1995, 2) weather events, and/or 3) somewhat later gypsy moth population development, high levels of fungal-induced mortality occurred earlier in the gypsy moth season than in the previous year. Most gypsy moth larvae died in a mid-season wave of fungal-induced mortality, with necropsied cadavers containing only conidia. This resulted in relatively few larvae surviving to late instars. At this time, a second, late-season, wave of fungus-induced mortality occurred, with over half of the necropsied cadavers now containing resting spores. The depletion of the gypsy moth population by the early appearance of the fungus apparently suppressed the second wave of NPV, which virtually disappeared from late-season larval collections from all plots.