Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2007
Publication Date: 4/1/2008
Citation: Lacey, L.A., Headrick, H.L., Arthurs, S.P. 2008. The Effect of Temperature on the Long Term Storage of Codling Moth Granulovirus Formulations. Journal of Economic Entomology 101(2):288-294.
Interpretive Summary: Codling moth, Cydia pomonella (L.), is the major pest of apple,pear and walnut in the Western United States and many other regions of the world. The codling moth granulovirus offers an alternative to broad spectrum insecticides and provides a selective and safe means of codling moth control with a negligible pre-harvest interval. Researchers at the USDA-ARS Yakima Agricultural Research Laboratory are studying ways to improve the efficacy and long term stability and storage of this virus. A range of storage and temperatures were evaluated from minus 20 to 35 degrees C for up to twelve months. Best results were obtained at the lowest storage temperature, and storage at 35 degrees C was most detrimental. These results provide guidance to commercial producers and marketers of the virus to maintain optimum virus effectiveness.
Technical Abstract: We assessed the long-term stability and storage potential of two commercial formulations of the codling moth granulovirus (CpGV), ‘Cyd-X’ and ‘Virosoft’. All assays were performed with individual neonate larvae in 2 ml vials on 1 ml of artificial larval diet that was surface inoculated with 10 'l of the test virus suspension. Baseline quantitative assays for the two formulations revealed that the LC50 and LC95 values (occlusion bodies/vial) did not differ significantly between the formulations. For year-long storage studies on Cyd-X viability after maintaining the virus at -20, 2, 25 and 35 °C, quantitative bioassays were conducted after 0, 3, 6, and 12 months storage. Cyd-X maintained good larvicidal activity from -20 to 25 °C, and was least negatively affected at the lowest temperature. Storage of Cyd-X at 35°C was markedly detrimental to its larvicidal activity even after just 3 months of storage. For longer term storage studies, Cyd-X and Virosoft formulations were stored at 2, 25 and 35ºC and assayed for larvicidal activity over a three year period. For recently received product, a 10 'l sample of a 10-5 dilution of both formulations resulted in 95-100% mortality in neonate larvae. Larvicidal activity for the Cyd-X formulation remained essentially unaffected for 156 weeks when stored at 2 and 25°C, but began to decline significantly after 20 weeks of storage at 35°C. The Virosoft formulation stored at 2°C also remained active throughout the 3 year study, but began to decline in larvicidal activity after 144 weeks at 25°C and 40 weeks at 35°C.