Bioassay of a nucleopolyhedrosis virus of the gypsy moth, Porthetria dispar

Abstract

The pathogenicity of an American isolate of the nucleopolyhedrosis virus of Porthetria dispar was studied. Laboratory data on third-instar larvae showed that mortality was directly related to virus concentration. The computed LD50 was 1,729 PIBs/larva or 72 PIBs/mg larval body weight. The LT50's for 2.5 × 106, 2.5 × 105, 2.5 × 104, 5 × 103, and 2.5 × 103 PIBs/larva were 8.1, 9.9, 11.3, 12.2, and 13.1 days, respectively. Approximately 37 and 60% of the total larval mortality occurred during the third- and fourth-instar, respectively. The periods to pupation and the pupal weights of survivors apparently were not affected by virus concentration. Moth emergence from surviving pupae was not reduced. © 1974.