Parasites and Pathogens of the Fall Webworm in Illinois

Naturally occurring parasites and pathogens of Hyphantria cunea (Drury) were recovered from field-collected larvae from northern, central, and southern Illinois in 1970. The following parasites were reared from these larvae: Sinophorus validus (Cresson), Meteorus hyphantriae Riley, Apanteles hyphantriae Riley, Elachertus hyphantriae Crawford, and Mericia ampelus (Walker). Total parasitism ranged from 34 to 39% from both the orange-headed and black-headed races of H. cunea . Three microsporidia, Nosema necatrix Kramer, Nosema sp., and Pleistophora schubergi hyphantriae Weiser, all new North American records for this host, and 1 nuclear polyhedrosis virus also were found. The most common pathogen was N. necatrix. Of the colonies sampled, 43% were infected with at least 1 of the 4 pathogens mentioned.