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Title: HOST PLANT EFFECTS ON THE ACTIVITY OF SELECTED NUCLEAR POLYHEDROSIS VIRUSESAGAINST THE CORN EARWORM AND BEET ARMYWORM (LEPIDOPTERA:NOCTUIDAE)

Author
item Farrar, Robert
item RIDGWAY, RICHARD - RETIRED

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/1999
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, each of which infects only a certain few species of insects or other arthropods. They are promising alternatives to pesticides for many important pests, especially caterpillars. They are usually sprayed onto crop plants, where insects eat them, become infected, and die. However, NPVs seem to work better on some species of plants than on others. We tested the activity of NPVs against two important pests, the corn earworm and beet armyworm, on different plants. With the corn earworm, the number of insects killed by viruses was greatest on corn, least on cotton, and intermediate on snap beans. With the beet armyworm, viruses killed the most insects on tomato, the fewest on cotton, and an intermediate number on collard. We expect our results to be useful to persons looking for non-chemical controls for pests. Our results suggest that NPVs would be more appropriate choices on some crops, such as corn, tomato, beans, or collard, than on other crops, such as cotton. Making better choices should lead to the development of effective and economical use patterns for NPVs in practical insect pest management programs. This can, in turn, reduce the use of chemical pesticides and problems of contamination, worker exposure, and residues.

Technical Abstract: The activity of the nuclear polyhedrosis virus (NPV) of the celery looper, Anagrapha falcifera (Kirby), (AfMNPV) against the beet armyworm, Spodoptera exigua (Hubner), was greatest when the virus was fed to larvae on foliage of tomato, least on cotton, and intermediate on collard. Activity of AfMNPV against the corn earworm, Helicoverpa zea (Boddie), was greatest on corn, least on cotton, and intermediate on bean. Survival times of larvae that were killed by virus were usually shorter on treatments on which rates of mortality were higher, but these differences were usually small, no more than one day. Effects of plants on viral activity do not appear to be strongly influenced by larval feeding rates. Effects of host plants on viral activity were not specific to AfMNPV; cotton and collard affected AfMNPV and the homologous NPV of the beet armyworm to similar degrees. Similar results were found for AfMNPV and the homologous NPV of the corn earworm on cotton and bean.