Trichoplusia ni(Hubner) annually suffers a massive epizootic caused by nuclear polyhedrosis viruses on the eastern seaboard of the United States. The examination of cabbage from 5 supermarket chain stores near Washington, D.C., showed that this epizootic begins in September, peaks in October, and declines in November. The amount of viable virus on this cabbage was about 7 million polyhedra per square inch of head leaf at the peak of the natural epizootic. Consumers eating raw cabbage receive large amounts of these viruses annually.