Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2000
Publication Date: July 1, 2000
Citation: BEHLE, R.W., MCGUIRE, M.R., TAMEZ-GUERRA, P. EFFECT OF LIGHT ENERGY ON ALKALI RELEASE VIRIONS FROM ANAGRAPHA FALCIFERA NUCLEOPOLYHEDROVIRUS. JOURNAL OF INVERTEBRATE PATHOLOGY. 2000. v. 76. p. 120-126. Interpretive Summary: Alternatives to chemical pesticides are needed. Once such group of alternatives are viruses that infect and kill insects. Commercialization of a virus isolated from cabbage looper, an important insect pest, has been limited by the high cost of production and rapid loss of insecticidal activity when exposed to sunlight. In its natural form, infective particles called virions are coated with a protein. Each virion is capable of causing infection of a pest insect. It has been suggested that dissolving the protein would release the virions and improve insecticidal activity. Our results demonstrated that the released virions were more active that the natural virus when samples remained wet. When dried, as with an insecticide spray on a leaf, the released virions lost all insecticidal activity. Also, released virions lost activity faster than natural virus with the intact protein when exposed to simulated sunlight. This information is important to other scientists and biopesticide companies producing this virus.
Technical Abstract: We compared the insecticidal activity of occluded with non-occluded AfNPV AfNPV baculovirus made by dissolving the occlusion body (OB) with sodium carbonate. Droplet feeding and cotton leaf feeding bioassay techniques were used to determine the dose response against neonate Trichoplusia ni Hubner 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, non-occluded virus (NOV) was 20 times more active (LC50 = 4.8 x 10**3 occlusion body [OB]/ml, dissolved) than occluded virus (LC50 = 9.6 x 10**4 OB/ml) when the samples remained wet. However, NOV lost activity when air-dried and then tested both droplet (LC50 > 1.0 x 10**6 OB/ml) and plant (LC50 > 3.0 x 10**6 OB/ml) bioassays. Adding sucros to NOV prevented the loss of insecticidal activity when samples were dried. NOV with 2% sucrose had dose responses similar to occluded virus samples with or without sucrose in both droplet feeding and plant feeding assays. These results indicate that the OB protected the insecticidal activity of virions from the detrimental affects of drying. The OB also provided some protection from the detrimental effects of simulated sunlight (xenon) exposure. NOV samples exposed to xenon light tended to have greater loss pf insecticidal activity than did similar samples of occluded virus. Possible benefits of increased insecticidal activity from the use of non-occluded virus is probably not sufficient to offset the rapid loss of activity due to drying or light exposure.