June 05 - Present Professor and Extension Specialist for Crop Ecology, Department of Plant Sciences, University of California, Davis, CA

July 01 - June 05 Department Chair, Department of Environmental Horticulture, University of California, Davis, CA

July 97 - Present Professor and Extension Specialist for Crop Ecology, Department of Environmental Horticulture, University of California, Davis, CA

July 91 - June 97 Associate Professor and Extension Specialist for Crop Ecology, Environmental Horticulture, University of California, Davis, CA

Dec 89 - June 91 Assistant Professor and Extension Specialist for Crop Ecology, Environmental Horticulture, University of California, Davis, CA

July 83- Dec 84 Research Associate, Texas Agricultural Experiment Station, Texas A&M University, Temple TX.

May 83 - July 83 Visiting Assistant Professor, Department of Botany,  North Carolina State University, Raleigh, NC.

Jan 83 - May 83 Post Doctoral Research Associate, USDA/ARS, Department of Botany, North Carolina State University, Raleigh, NC.