Author
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FARRAR, ROBERT - UNIVERSITY OF MARYLAND |
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Ridgway, Richard |
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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/27/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Nuclear polyhedrosis viruses (NPVs) are naturally occurring viruses infect only insects and other arthropods. They are promising alternatives to chemical pesticides for many important insect pests, especially caterpillars. The recently discovered NPV of the celery looper (AfMNPV) kills a wider variety of caterpillars than do most other NPVs, and so is potentially more useful as a biological control agent. Other recent developments that increase the potential for the use NPVs include the development of technology for producing them in cell culture (in vitro) instead of in live insects (in vivo), and the discovery that certain fluorescent brighteners can increase the potency of at least some NPVs. However, there was a need for information on the potency of AfMNPV against several insect pests, to verify that AfMNPV produced in vitro was as potent as that produced in vivo, and to determine if fluorescent brighteners could work with AfMNPV as they had with other viruses. Tests showed that AfMNPV should be useful against the corn earworm and beet armyworm, but probably not the diamondback moth, that virus produced in vitro is comparable to that produced in vivo, and that the fluorescent brightener could improve the action of AfMNPV against all three pests. These results will facilitate the development of effective and economical biological pesticides based on AfMNPV and aid in defining their use patterns in practical insect management programs. Additional research is needed to determine effects of various ratios of AfMNPV and fluorescent brighteners under practical field conditions. Technical Abstract: The potency of the nuclear polyhedrosis virus of the celery looper, Anagrapha falcifera (Kirby), (AfMNPV), was evaluated against the second instars of three species of Lepidoptera, the corn earworm, Helicoverpa zea (Boddie), beet armyworm, Spodoptera exigua (Hubner), and diamondback moth, Plutella xylostella (L.). Potency was highest against the corn earworm, least against the diamondback moth, and intermediate against the beet armyworm. The potencies of in vivo and in vitro produced viruses compared favorably, though statistically significant differences were found. However, during the initial experiments, a bacterial contaminant, which adversely affected insects treated with the higher dosages of in vivo AfMNPV, was detected, and identified as Serratia marcescens Bizio. Studies using neomycin sulfate to control the bacterium indicated that the results with the in vivo produced virus were most affected by the S. marcescens in studies with the diamondback moth, where especially high dosages of AfMNPV were needed to kill that insect. The addition of a stilbenedisulfonic acid derivative, Blankophor BBH , to AfMNPV greatly increased the potency of the virus against all three insect species. Neither the use of neomycin sulfate nor Blankophor BBH altered the order of susceptibility among the three insect species. Rational is presented for using methods for quantifying survival time of insects and estimating oral uptake that have relatively high levels of precision. Such precision should increase the probability of designing improved methods for utilizing viruses in practical insect management programs. |
