Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2005
Publication Date: 7/15/2005
Citation: Lacey, L.A., Arthurs, S.P. 2005. New method for testing solar sensitivity of commerical formulations of the granulovirus of codling moth (Cydia pomonella, Tortricidae: Lepidoptera). Journal of Invertebrate Pathology. 90:85-90. Interpretive Summary: Codling moth is the most serious insect pest of apple in the Pacific Northwest. The traditional method for controlling this pest is through the routine application of broad spectrum insecticides. Options for codling moth control for organic growers has been limited. The recent registration of 3 commercial formulations of the codling moth granulovirus (CpGV) in the USA and their approval by the Organic Materials Review Institute expands the options for control of hatching larvae in organic orchards. It also provides conventional growers with an additional treatment. Among the biological control options available for codling moth, CpGV provides effective and selective control of larvae before or as they enter the apple. Researchers at the USDA-ARS Laboratory in Wapato, WA have developed methods and a protocol to investigate the effect of simulated sunlight, especially ultraviolet (UV) rays on CpGV and provided baseline information on the sensitivity of commercial CpGV products. This work sets the stage for future improvements to CpGV with UV-protectants. Use of CpGV will contribute significantly to the conservation of other natural enemies in the orchard agroecosystem. This microbial control agent will enhance and complement the control activity provided by mating disruption.
Technical Abstract: A method for screening codling moth granulovirus (CpGV) formulation sensitivity to sunlight using specially prepared half apples and a solar simulator is described. The half apple preparation allows an even coverage of virus over the surface of the fruit that would not be possible using whole apples. Leaves and artificial medium were not usable for extended periods of exposure in the solar simulator due to excess drying. Fruit was sprayed with 10-3 and 10-5 dilutions of three commercial formulations of CpGV (Carpovirusine, Cyd-X, and Virosoft) and infested with codling moth neonates. Half of the sprayed fruit was exposed to 765 watts/m2 for 4 hours in an Atlas Suntest CPS solar simulator resulting in an accumulated radiant energy of 1.08 x 107 joules/m2 before they were infested with neonate codling moth larvae. Spraying non-irradiated fruit with the10-3 dilution of Cyd-X and Virosoft resulted in nearly 100% mortality of neonate larvae. Irradiation reduced viral activity by 71-98% at the 10-3 dilution and by up to 32% at the 10-5 dilution relative to non-irradiated fruit. The procedures utilized enabled good preservation of the fruit throughout the incubation period and minimized invasion of the fruit by plant pathogens and saprophytic organisms. This laboratory method for screening candidate formulations and potential UV protectants could conserve time and resources by eliminating adjuvants with less potential in laboratory tests and field testing only the most promising candidates. It also enables year-round testing.