title: Effects of diet-age and streptomycin on virulence of Autographa californica M nucleopolyhedrovirus against the tobacco budworm.
abstract: Addition of the antibiotic streptomycin to two artificial diets routinely used in bioassays of neonate lar vae of Heliothis virescens (tobacco budworm) infected with Autographa californica M nucleopolyhedrovirus (AcMNPV) increased lethal times of the virus. After storage of diets for 3 weeks at 4 degrees C, lethal times of infected larvae were significantly slower compared to those for larvae bioassayed using diets stored for 2 weeks or less. The effect of diet-age on rate of mortality was not the result of a change in total protein content or pH of the diet, but was apparently the result of some other alteration in the quality of the diet (e.g. microbial spoilage, palatibility, and/or nutritional value unrelated to total protein). Although we did not determine why lethal times were slower in response to streptomycin concentration or diet-age, we did find that slower lethal times were correlated with slower relative growth rates (RGR) of infected larvae. In addition, RGR of infected larvae decreased as a function of increasing streptomycin concentration, diet-age, and the interaction of the two factors. These results demonstrate that it is difficult to obtain consistent and comparable bioassay results if antibiotic composition and diet-age are not controlled. We suggest a standardized diet or highly standardized procedures for a given diet be developed that permits comparison of bioassays among and within laboratories.
authors.affiliation: Department of Entomology, University of California, Davis, California, 95616, USA.
authors.forename: K
authors.initials: K
authors.lastname: Hoover
authors.forename: C M
authors.initials: CM
authors.lastname: Schultz
authors.forename: S S
authors.initials: SS
authors.lastname: Lane
authors.forename: B C
authors.initials: BC
authors.lastname: Bonning
authors.forename: B D
authors.initials: BD
authors.lastname: Hammock
authors.forename: S S
authors.initials: SS
authors.lastname: Duffey
mesh_terms: D000818:Animals; D003588:Cytopathogenic Effect, Viral; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D007814:Larva / Q000254:growth & development / Q000821:virology; D017924:Nucleopolyhedroviruses / Q000472:pathogenicity*; D012044:Regression Analysis; D018411:Spodoptera / Q000821:virology*; D013307:Streptomycin / Q000494:pharmacology*
chemical_list: D013307:Streptomycin