Secondary transmission of nuclear polyhedrosis virus by Pseudoplusia includens and Anticarsia gemmatalis larvae on semisynthetic diet

Abstract

Secondary transmission of nuclear polyhedrosis viruses of the soybean looper, Pseudoplusia includens (SLNPV), and velvetbean caterpillar, Anticarsia gemmatalis, in their respective hosts on semisynthetic diet was examined. Mortality of test P. includens larvae (untreated), reared together on diet with SLNPV-treated (primary infected) P. includens larvae (at all sizes), was higher than in test A. gemmatalis larvae reared with primary infected A. gemmatalis larvae. Removal of primary infected larvae from rearing containers within 24 hr of death resulted only in low mortality levels in the test larvae of both species. Larval mortality of both species increased with the length of time that larvae were exposed to cadavers of primary infected larvae. In both species mortality differed with size of untreated larvae, size at death of primary infected larvae, and stage of disease in primary infected larvae when they were placed with the untreated larvae. However, the effect of each factor on secondary transmission differed somewhat with insect species.