DOSAGE-MORTALITY DATA ON A NUCLEAR-POLYHEDROSIS VIRUS OF BOLLWORM HELIOTHIS ZEA

The need for a reliable method of estimating the virulence (potency) of a nuclear-polyhedrosis virus of the bollworm, Heliothis zea, is discussed. Dosage-mortality data is obtained from a simple reproducible bioassay technique. Early third-instar larvae, averaging 20 mg in weight, were used throughout this study; the larvae were held at 28° ± 2°C throughout the testing period. The calculated ld50 values in terms of polyhedral inclusion bodies (PIB) per larva for three different Heliothis viruses (Biotrol®, Sudan, and Ivory Coast) were 269, 344, and 459, respectively. Laboratory data show that Biotrol® Heliothis zea nuclear-polyhedrosis virus is more virulent than the other two viruses when tested on the larvae of Heliothis zea. © 1969.