2013 Annual Report
The goal of the project is to improve the efficacy of the granulosis virus for codling moth. The virus is selective for codling moth and its use does not disrupt management of secondary pests in the orchard, and the material is a registered organic product. The technical objectives wee to 1. Evaluate several potential additives to improve the performance of the virus. These included a wild yeast collected from codling moth larvae within apples, and a commercial bread yeast. Laboratory assays and field trials were conducted to assess their relative performance. A Metschnikowia sp. yeast collected from codling moth larvae enhanced larval survival and accelerated larval development within yeast-treated apples compared with surface sterilized fruits. The addition of the Metschnikowia sp. yeast with cane sugar significantly improved the efficacy of a codling moth granulosis virus (CpGV) insecticide in laboratory bioassays. Three additional species of yeast were isolated from codling moth field-collected larvae and were found to also improve the insecticidal performance of CpGV in laboratory bioassays. Other materials, such as active bread yeast with sugar, the amino acid L-aspartate with sugar, and the Monterey Insect Bait were found to be very effective in improving the insecticidal activity of the CpGV in laboratory bioassays. Monosodium glutamate with or without sugar was not very effective in similar bioassays. Field trials with Metschnikowia sp. yeasts and bread yeast, both with sugar, increased codling moth larval mortality and reduced fruit injury in a season-long virus spray program. The addition of microencapsulated pear ester did not improve the efficacy of CpGV applications. Fruit injury from San Jose Scale was significantly reduced with the applications of the yeasts plus sugar. The sum of these experiments is that the use of active yeasts with sugar can improve the efficacy of the virus insecticide. This improved performance can translate to greater use by both organic and conventional growers. Further adoption of the virus can replace the more traditional use of synthetic insecticides and help to minimize their disruptive effects on the biological control of a suite of secondary pests found in orchards.