YIELD OF OCCLUSION BODIES FROM FOREST TENT CATERPILLAR (LEPIDOPTERA: LASIOCAMPIDAE) LARVAE INFECTED WITH A NUCLEAR POLYHEDROSIS VIRUS

Abstract

The forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), is subject to a variety of naturally occurring infectious diseases, including a nuclear polyhedrosis virus (MdNPV) which has been observed to reach epizootic proportions (Stairs 1966; Myers 1993).Because MdNPV is currently available only in limited quantities for small-scale experimentation, production scale-up is vital to it's potential as a biological control agent against the forest tent caterpillar. Viruses replicate only in living cells, therefore it is necessary to produce viral insecticides either in host insect larvae (in vivo) or in susceptible cell cultures (in vitro). Insect cell cultures have not yet been developed so that large-scale production of baculoviruses are feasible (Cunningham 1995), thus in vivo production must be used. To plan for the scale-up of NPV production, it is necessary to establish the yield of occlusion bodies (OBs) from M. disstria larvae. We report here the yield of OBs from four larval instars inoculated with MdNPV, the time to mortality, head capsule widths, and body weights, and recommend larval instars suitable for further research toward commercial-scale production.