Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2013
Publication Date: 8/25/2013
Citation: Knight, A.L., Witzgall, P. 2013. Combining mutualistic yeast and pathogenic virus - a novel method for control for codling moth control. Journal of Chemical Ecology. 39:1019-1026. Interpretive Summary: Development of new techniques to improve the performance of selective Biocontrol agents, such as granulosis virus for codling moth remains an important objective in tree fruit pest management. Studies conducted by researchers at the USDA, ARS, Yakima Agricultural Research Laboratory, Wapato, WA in combination with researchers at the Swedish University in Alnarp Sweden have identified a mutualistic relationship between natural yeasts and codling moth in apple. Combining a natural yeast and sugar with the granulosis virus has significantly improved the potency of the virus to kill larvae before they penetrate and damage fruits. Use of the yeast and sugar can improve the management of codling moth without growers having to rely on more broad-spectrum insecticide chemistries that can disrupt other pests.
Technical Abstract: Studies evaluated the lethal effectiveness of combining yeasts isolated from larvae of codling moth, Cydia pomonella (L.) with the codling moth granulosis virus (CpGV). Apples were treated with CpGV and three yeast species, including Metschnikowia pulcherrima Pitt and Miller, Cryptococcus tephrensis Vishniac, and Aureobasidium pullulans (de Barry) Arnaud, added alone or in combination with brown cane sugar. The addition of sugar to CpGV did not significantly increase larval mortality. The addition of yeasts to CpGV significantly increased larval mortality compared with CpGV alone. The three yeasts did not differ in their levels of activity with CpGV, and increasing their concentration did not improve efficacy. The addition of sugar with either M. pulcherrima or C. tephrensis to the CpGV significantly increased larval mortality and the proportion of uninjured fruits compared with CpGV alone. The proportion of fruit suffering injury and survival of larvae were significantly reduced in a field trial with the addition of M. pulcherrima and sugar to CpGV compared with the untreated control and CpGV alone. In addition, fruit injuries from the tortricid leafroller Pandemis pyrusana Kearfott, and San Jose Scale Quadraspidiotus perniciosus (Comstock) were reduced on trees treated with CpGV plus yeast and sugar compared with the untreated control perhaps due to the physical dislocation of insects by the hand-gun spray application. These data support the need for additional chemical, behavioral, and efficacy studies of yeast – insect pest interactions to develop new approaches to enhance microbial insecticides.