The influence of infections of nuclear-polyhedrosis virus on adult cabbage loopers and their progeny

Abstract

The longevity, mating, and oviposition of adult cabbage loopers ( Trichoplusia ni) infected with nuclear-polyhedrosis virus were not affected, even when high titers of virus were used; infection occurred only when the virus was injected into the hemocoel. Histological examination of diseased adults revealed infected nuclei in the tracheal matrix cells but rarely in the fat body, hypodermis, or other tissues that are infected at the larval stage. Viability of eggs was significantly reduced (to less than 10%) the first few days after treatment when 1-day-old female moths were injected with the virus, but this effect decreased with dilution. Also, the effect was less when the female was older at the time of infection. Examination of dead eggs showed that embryological development had commenced. The large numbers of progeny reared from moths that were injected with the virus rarely showed infection, indicating that transovarian transmission of the virus did not occur. In contrast, progeny of moths fed the polyhedra were often infected though the effect was unpredictable and could be eliminated by surface-sterilization of the eggs.