|Witzgall, Peter - Swedish University Of Agricultural Sciences|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2015
Publication Date: 4/1/2015
Citation: Knight, A.L., Witzgall, P. 2015. Improving the performance of the Granulosis virus of Codling moth (Lepidoptera: Tortricideae) by adding the yeast Saccharomyces cerevisiae with sugar. Environmental Entomology. 44(2):252-259. Interpretive Summary: Codling moth is the most important insect pest of apples in the world and growers rely heavily on insecticides to manage this pest at low levels. The most ecological benign insecticide used for codling moth is the granulosis virus , a specific pathogen for just this insect. Unfortunately, the virus has several weaknesses that limit its use and effectiveness. Field and laboratory studies conducted by researchers at the USDA, ARS, Yakima Agricultural Research Laboratory, Wapato, WA with collaboration with researchers at the Swedish University in Alnarp Sweden showed that the simple of addition of sugar and brewer’s yeast could improve the performance of the virus by killing a greater proportion of larvae before they damage fruits. These findings can improve the management of codling moth without growers having to rely on more broad-spectrum insecticide chemistries that can disrupt other orchard pests and require growers to apply additional sprays.
Technical Abstract: Studies evaluated the effectiveness of adding Saccharomyces cerevisiae with brown cane sugar (sugar) to the codling moth granulosis virus, CpGV, to improve larval control of Cydia pomonella (L.), on apple. Neither the use of the yeast or sugar alone caused larval mortality greater than the water control in laboratory bioassays. The addition of sugar to CpGV did not significantly increase larval mortality. The addition of S. cerevisiae to CpGV significantly increased larval mortality compared with CpGV alone. Increasing the concentration of yeast or sugar from 1.2 to 3.6 g L-1 did not improve the efficacy of CpGV. The combination of S. cerevisiae and sugar with CpGV significantly increased larval mortality compared with CpGV with either additive alone. The effectiveness of adding S. cerevisiae and sugar to CpGV was similar to the benefit of adding similar rates of Metschnikowia pulcherrima (isolated from codling moth larvae) and sugar. The proportion of uninjured fruit was significantly increased with the addition of S. cerevisiae and sugar to CpGV compared with CpGV alone and an untreated control in a field trial in 2012, but only from a water control in 2013; however, larval mortality was significantly increased in both years. The numbers of live overwintering larvae in cardboard bands placed on trees was significantly reduced from the control following a seasonal program of CpGV plus yeast and sugar. The addition of a microencapsulated formulation of pear ester did not improve the performance of CpGV alone or CpGV plus yeast and sugar.