Efficacy and persistence of a granulosis virus against infestations of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) on raisins

Laboratory tests were conducted on the temperature stability of a formulation of a granulosis virus of Plodia interpunctella (Hübner). Efficacy of the formulation on raisins during extended high temperature storage was of particular interest as was the ability of the formulation to control incipient populations in the commodity. Two concentrations of the formulation were tested at temperatures of 27, 32, and 38°C storage for 0, 1, 3, 6, and 12 months to determine the influence of temperature on efficacy. The efficacy against previously infested raisins was determined at 27°C and with three concentrations of the formulation. The studies confirm the high level of control that can be obtained with this virus. At 32 and 38°C efficacy was substantially reduced after 1–3 months in storage. However, raisins would rarely be subjected to these higher temperatures for long periods without affecting quality. When incipient populations were treated, varying degrees of control were obtained depending on dosage and the age of larvae at the time of treatment. Control of the survivor's progeny was at least as good as that of the originally treated insects.