Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/1995
Publication Date: N/A
Citation: N/A Interpretive Summary: There have been efforts over the last decade to expand the host range, virulence, or rate of mortality of some microbial insecticides using novel biotechniques. Field persistence of the insecticidal activity under sunlight-ultraviolet may be as, or more important than efforts to enhance activity of a viral insecticide. All commercial microbial insecticides (those made from safe, noninfectious, non-toxic viruses, bacteria and fungi) are extremely sensitive to sunlight ultraviolet. We wanted to know whether genetically engineered strains of an experimental commercial viral insecticide were more, or less, sensitive to sunlight than that of a natural wild type. Our results showed that genetic engineering did not result in the viruses being more sensitive to sunlight-UV than the natural wild-type virus. Since it is too early to generalize we recommend that the environmental stability of each newly modified viral insecticide should be determined if they are to be successfully used to control field populations of pest insects.
Technical Abstract: There have been efforts over the last decade to expand the host range, virulence, or rate of mortality of baculoviral insecticides via genetic insertion of genes expressing alien toxins, enzymes or hormones. Persistence of the inherent insecticidal activity under sunlight-ultraviolet, however, may be as, or more significant than efforts to enhance activity of a viral insecticide. None of three recombinants (AcAaIT, AcJHE-KK, AcJHE-SG), exposed to simulated sunlight (SUV) were significantly more or less sensitive to SUV than the parental, wild-type clone AcC6. The % original activity remaining (% OAR) of the recombinants AcAaIT, AcJHE-KK, AcJHE-SG and the parental AcC6 average 50.3 + or - 8.7, 55.8 + or - 8.1, 43.0 + or - 10.5, and 51.8 + or - 7.5 percent, respectively. The 1/2-life (3 to 4 h) of all recombinants and the parental isolate was within that previously reported for other baculoviruses. Rate of larval mortality was significantly faster with the recombinants AcAaIT than with the wild-type parental AcC6 or the recombinant AcJHE-SG. The LT-50 (in days) for each of the strains was: AcC6, 4.3; AcJHE-SG, 4.3; AcJHE-KK, 4.2; and AcAaIT, 3.0 days. Genetic engineering did not result in the recombinants being more or less sensitive to SUV than the parental wild-type. It is too early to generalize from these specific results for all engineering processes such as gene deletion, host range expansion, replacement of polyhedrin or replacement of p10. Thus, environmental stability of each novel, genetically modified baculovirus should be individually determined if they are to be successfully used to control field populations of pest insects.