2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Trust agreement between ARS and the Almond Board of California. Additional details of the research can be found in the report for the parent project 5542-21000-014-00D, Improving Pollination Rates by Increasing Colony Populations and Defining Pollination Mechanisms. Plant essential oils were selected for starch encapsulation based on their ability to control Varroa mites. Preliminary data obtained in 2005 indicated that Thymol, Origanum, Clove and Cinnamon were the most effective. The essential oils were microencapsulated by ARS chemists at the USDA Bioproducts Laboratory in Albany, CA. so that they could be fed to bees without toxic side effects. The microencapsulated essential oils were mixed with powdered sugar and fed to bees by a commonly known method used by beekeepers to apply antibiotics called dusting. Following microencapsulation, Clove and Thymol were the most effective in controlling invasion and reproduction in the cells as well as mite drop rates. The optimum concentration to be used in the treatment was 2.5%. Even though the delivery system works well, we need to improve the release rate of the oils.