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Effect of light energy on alkali-released virions from Anagrapha falcifera nucleopolyhedrovirus
R W Behle1, M R McGuire, P Tamez-Guerra
1Bioactive Agents Research Unit, United States Department of Agriculture, Agricultural Research Center, National Center for Agricultural Utilization Research, Peoria, Illinois 61604, USA. behlerw@mail.ncaur.usda.gov
Abstract:
We compared the insecticidal activities of occluded and nonoccluded AfMNPV baculovirus obtained by dissolving the occlusion bodies (OB) with sodium carbonate. Droplet feeding and cotton leaf feeding bioassay techniques were used to determine the dose response against neonate Trichoplusia ni (Hübner) and loss of insecticidal activity when the virus was exposed to simulated sunlight from a xenon light source. Using droplet bioassays to determine a dose response, nonoccluded virus (NOV) was 20 times more active (LC(50) = 4.8 x 10(3) OB/ml, dissolved) than occluded virus (LC(50) = 9.6 x 10(4) OB/ml) when the samples remained wet. However, NOV lost activity when air dried before being tested by droplet (LC(50) > 1.0 x 10(6) OB/ml) or leaf feeding (LC(50) > 3.0 x 10(6) OB/ml) bioassays. Adding sucrose to NOV prevented the loss of insecticidal activity when samples were dried. The activity of NOV with 2% sucrose was similar to that of occluded virus samples, with or without sucrose, in both droplet feeding and leaf feeding assays. These results indicate that the OB protected the insecticidal activity of virions from the detrimental effects of drying. The OB also provided some protection from the detrimental effects of simulated sunlight (xenon) exposure. NOV samples exposed to xenon light had significantly greater loss of insecticidal activity than did similar samples of occluded virus. Without advancement in technologies, such as formulations, possible benefits of increased insecticidal activity from the use of nonoccluded virus is probably not sufficient to offset the rapid loss of activity due to drying or light exposure.
Insights
Occlusion bodies (OB) protect baculovirus insecticidal activity from drying and sunlight. Nonoccluded virus (NOV) is more potent but unstable, requiring formulations like sucrose for practical application against pests like Trichoplusia ni.
Area of Science:
- Entomology
- Virology
- Pest Management
Background:
- Baculoviruses are crucial biological control agents.
- AfMNPV baculovirus exists in occluded (OB) and nonoccluded (NOV) forms.
- Understanding virion stability is key for effective pest control.
Purpose of the Study:
- Compare insecticidal activity of occluded vs. nonoccluded AfMNPV.
- Assess virion stability under drying and simulated sunlight.
- Evaluate the role of OB in protecting insecticidal efficacy.
Main Methods:
- Dissolved OB with sodium carbonate to obtain NOV.
- Used droplet feeding and cotton leaf feeding bioassays.
- Tested dose response against neonate Trichoplusia ni.
- Exposed virus samples to simulated sunlight (xenon).
Main Results:
- NOV showed 20x higher activity than OB when wet.
- NOV lost significant activity upon drying; sucrose addition prevented this.
- OB protected virions from drying and simulated sunlight damage.
- NOV exposed to light lost more activity than OB.
Conclusions:
- Occlusion bodies are vital for baculovirus stability and field efficacy.
- NOV's enhanced potency is offset by instability without protective formulations.
- Formulation strategies are necessary to harness NOV benefits in pest control.