Relative Potency of Selected Nuclear Polyhedrosis Viruses Against Five Species of Lepidoptera1, 2

Robert R. Farrar, Jr. and Richard L. Ridgway3

USDA, Agricultural Research Service
Insect Biocontrol Laboratory
Bldg. 011A, BARC-West
Beltsville, Maryland 20705 USA

J. Agric. Urban Entomol. 16(3): 187-196 July 1999

ABSTRACT

    The potencies of two or three nuclear polyhedrosis viruses (NPVs), selected from among those of alfalfa looper, Anagrapha falcifera (Kirby), AfMNPV; celery looper, Autographa californica (Speyer), AcMNPV; corn earworm, Helicoverpa zea (Boddie), HzSNPV; and beet armyworm, Spodoptera exigua (Adubner), SeMNPV, were compared in side-by-side bioassays against five insect species. Each insect species was tested at a different time, but, for each species all viruses were tested at the same time. Against the corn earworm, HzSNPV was the most potent; AcMNPV, the least potent; and AfMNPV, intermediate in potency. AcMNPV, AfMNPV, and HzSNPV were of similar and high potency against the tobacco budworm, Heliothis virescens (F.). SeMNPV was more potent than either AcMNPV or AfMNPV against the beet armyworm. AcMNPV and AfMNPV were of similar low potency against the fall armyworm, Spodoptera frugiperda (J. E. Smith). AcMNPV was more potent than AfMNPV against the diamondback moth, Plutella xylostella (L.). Among dosages that were included for more than one virus against the same insect species, no significant differences between viruses in speed of kill were seen. Increasing virus dosage slightly increased speed of kill for HzSNPV against H. zea and for AfMNPV against S. frugiperda, but had no significant effect on speed of kill for other virus/insect combinations. These results should be useful both in the selection of natural virus strains for use against particular pests, and in the selection of viruses as candidates for genetic engineering to improve their speed of action.

KEY WORDS
    Helicoverpa zea, Heliothis virescens, Lepidoptera, Noctuidae, Nuclear polyhedrosis virus, Plutellidae, Plutella xylostella, potency, Spodoptera exigua, Spodoptera frugiperda

1Accepted for publication 30 June 1999.
2This article reports results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation by USDA for its use.
3Present address: BioManage Services, 2229 Countryside Dr., Silver Spring, Maryland 20905-4520.