Prey selection and baculovirus dissemination by carabid predators of Lepidoptera

Abstract

Abstract. The interaction between coleopteran predators and baculovirus‐infected larvae was studied in the laboratory and the field in order to assess the potential role of predators in the dissemination of a nucleopolyhedrovirus (NPV). Preference tests using three carabid species, Harpalus rufipes De Geer, Pterostichus melanarius Illiger and Agonum dorsale Pont, showed no evidence of discrimination between healthy and diseased larvae of the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae) as prey items. Virus infectivity was maintained after passage through the predator's gut. NPV mortality ranged from 97% to 20% when test larvae were exposed to faeces collected immediately after and 15 days post‐infected meal respectively. The potential for transfer of inoculum in the environment was estimated in the laboratory by soil bioassay. Carabids continuously passed infective virus to the soil for at least 15 days after feeding on infected larvae. Field experiments showed that carabids which had previously fed on diseased larvae transferred sufficient virus to the soil to cause low levels of mortality in larval populations of the cabbage moth at different instars.