Natural mortality of the gypsy moth along a gradient of infestation

Natural mortality of gypsy moth [Lymantria dispar (L.) (Lepidoptera: Lymantriidae)] eggs, larvae, and pupae was examined at several locations along a gradient of infestation in Ontario, Canada. Most mortality of eggs was the result of exposure to winter weather. This mortality was mitigated in egg masses located near ground level where they benefited from snow cover. At least six species of parasitoids were found attacking gypsy moth larvae and pupae. The most common species were present in the same rank order of abundance at all sites. Identified pathogens were also present in most sites but their relative abundance varied greatly. The mycopathogen Entomophaga maimaiga Humber, Shimazu & Soper (Zygomycetes: Entomophthorales) was found at all sites and usually was responsible for the highest levels of observed, single-source mortality at the site.