Current research centers on biology and control of fungal diseases of grapes, with current emphasis on powdery and downy mildew, and Botrytis bunch rot. Also, the epidemiology of boxwood blight.
Grapes are one of the fastest growing crops in Virginia, now over 2000 high-value acres, and are considered one of the best alternatives to crops for which profitability has been declining. However, in our humid climate, grape diseases are a constant concern. The most economically profitable varieties of grape are highly susceptible to several diseases, and for this reason grape crops are treated with frequent fungicide sprays. These intensive spray programs and the highly selective nature of modern fungicides entail a serious risk of pathogens becoming resistant to some fungicides. Currently, the only way for a grower to find out that such resistance has developed is to experience a disease control failure, which may cause severe crop loss and even complete crop failure.
Surveys conducted by my lab have discovered that grape downy mildew had developed resistance to strobilurin fungicides in many Virginia locations. Strobilurin fungicides have played a major role in grape disease management programs in recent years, and this was the first detection of this type of resistance in grape downy mildew in North America. In addition, powdery mildew resistance to this group was also found in many locations. We have also measured the sensitivity of grape powdery mildew populations to sterol-inhibiting fungicides, another key group, and have documented that reduced sensitivity to the most commonly used compounds is widespread. One case of quinoxyfen resistance of grape powdery mildew is alos being investigated. A recent survey of Botrytis cinerea, the cause of grape bunch rot, revealed the presence in many vineyards of resistance to strobilurins, boscalid, the benzimidazoles, the anilinopyrimidines (cyprodinil and pyrimethanil), and to a much lesser extent fenhexamid.
Our lab also participates in research on boxwood blight and mango anthracnose. Boxwood blight was detected for the first time in the United States in 2011 in North Carolina, Virginia and Connecticut, and has since spread to many states. It is a devastating disease in historic landscapes and in production nurseries. Our research aims to clarify the epidemiology of the disease, and develop strategies to minimize its impact. Further details about this disease may be found on the website maintained by the Virginia Boxwood Blight Task Force.
Ph.D., Plant Pathology, University of California, Riverside, 1981
M.S., Wageningen University, The Netherlands, 1975
2016: College Certificate of Teaching Excellence, College of Agriculture and Life Sciences, Virginia Tech
I contribute to outreach to grape growers (communicate research findings and general education on plant diseases and their management), landscape and garden interests (boxwood blight), and master gardener training.