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Title: RELATIVE POTENCY OF SELECTED NUCLEAR POLYHEDROSIS VIRUSES AGAINST FIVE SPECIES OF LEPIDOPTERA

Author
item FARRAR, ROBERT
item RIDGWAY, RICHARD - RETIRED

Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Commercial agriculture continues to rely heavily on chemical pesticides for insect pest control, despite problems with environmental contamination, worker exposure, and residues in agricultural products. Nuclear polyhedrosis viruses (NPVs) are naturally occurring viruses that infect only insects and some other arthropods. They are promising alternatives to pesticides for many important pests, especially caterpillars. Several NPVs are under commercial development, or are candidates for commercial development, as biological pesticides. These include the NPVs of the celery looper (AfMNPV), the alfalfa looper (AcMNPV), the corn earworm (HzSNPV), and beet armyworm (SeMNPV). However, in order for growers to select the most efficacious viruses for use on their crops, data comparing these viruses in side-by-side tests are needed. Toward this end, we compared different viruses against five important pest caterpillars: the corn earworm, tobacco budworm, fall armyworm, beet armyworm, and diamondback moth. Distinct differences among viruses were found. These results will aid in the development of effective and economical use patterns for NPVs in practical insect pest management programs. This will, in turn, reduce the use of chemical pesticides and problems of contamination, worker exposure, and residues.

Technical Abstract: The potencies of two or three nuclear polyhedrosis viruses (NPVs), selected from among those of the alfalfa looper, Anagrapha falcifera (Kirby), (AfMNPV), the celery looper, Autographa californica (Speyer), (AcMNPV), the corn earworm, Helicoverpa zea (Boddie), (HzSNPV), and the beet armyworm, Spodoptera exigua (H¿bner), (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. 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 but low potency against the fall armyworm, Spodoptera frugiperda (J. E. Smith). AcMNPV was more potent than AfMNPV against the diamondback moth, Plutella xylostella (L.). Those viruses that were the most potent generally also killed their hosts faster than did the other viruses. In most cases, increasing dosage also resulted in faster kill. However, differences in speed of kill were usually small (less than 1 d) and thus may not be of practical importance in pest management programs. 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.