Overwintering of Trichogramma nubilale in Delaware

Field studies conducted during the winters of 1972–73, 1973–74 and 1975–76 show that Trichogramma nubilale Ertle and Davis is capable of overwintering in eggs of its preferred host, the European corn borer, Ostrinia nubilalis (Hubner), in Delaware. A period of conditioning, and development to a critical life stage (i.e., pupa), appears necessary for this parasite to successfully overwinter. Adult emergence in the spring occurs from late-March to late-April.