SUBLETHAL EFFECTS OF BACULOVIRUS IN THE CABBAGE MOTH, MAMESTRA-BRASSICAE

Sublethal effects of pathogens such as baculoviruses, in particular ve rtical transmission to subsequent host generations, may play an import ant role in their ecology and population dynamics and could also be of relevance in their use as pest control agents. The effects of a range of sublethal concentrations of a nuclear polyhedrosis virus (NPV) wer e investigated in fourth and fifth instar larvae of the cabbage moth, Mamestra brassicae. Survivors of the NPV inoculation exhibited an exte nded developmental time in both the larval and the pupal phase compare d with control larvae. There was a general trend toward increasing dev elopmental time with increasing viral concentration. Pupal weight, sex ratio, fecundity, and egg viability were not significantly different between insects subjected to viral challenge and control groups. A low level of NPV mortality (0.55%) was recorded in the progeny of adults which had developed from larvae subject to viral challenge. Viral deat h in progeny larvae occurred predominantly during the second instar. V ertical transmission, although occurring at low levels, may be vital f or the long-term persistence of the virus, particularly in a mobile pe st species such as M. brassicae, which occupies ephemeral habitats. (C ) 1995 Academic Press, Inc.