Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 3, 1996
Publication Date: N/A
Interpretive Summary: Wild strains of insect viruses have been genetically engineered in attempts to enhance their effectiveness as safe viral insecticides. But how much more effective are these engineered strains than the natural, wild strains? We found that an engineered strain killed an insect pest ca. 25% faster than the wild strain and that the dose of the wild strain would have to be increased ca. 8-16 times to match the effectiveness of the engineered strain. Comparative guidelines of this kind should help scientists engineering insect viruses as well as producers and growers interested in their development as safe, effective viral insecticides.
Technical Abstract: A parental, wild-type strain of the nuclear polyhedrosis virus of Autographa californica (AcMNPV) and two recombinant strains, engineered to express a scorpion toxin (AcAaIT) and a juvenile hormone esterase (AcJHE-KK), were used. Initial mortality of 1st-, 4th- and 5th-instar larvae, regardless of the polyhedral inclusion body (PIB) concentration, was not detected until the 2nd day of exposure. At equivalent concentrations of virus the recombinant AcAaIT was the fastest acting (had the lowest LT-50) strain followed by the recombinant AcJHE-KK and lastly the wild-type AcC6. There was no significant difference in larval mortality between the virus treatments (regardless of the viral strain, the larval stage, or the PIB concentration) after the 5th day of exposure. Each doubling of the viral concentration of AcC6 decreased the LT-50 by ca. 5%. Therefore, an 8- to 16-fold increase in the concentration of virus of the wild-type AcC6 was needed to attain an LT-50 equivalent to that of the recombinants AcAaIT and AcJHE-KK.