Current research centers on biology and control of fungal diseases of grapes, with current emphasis on powdery and downy mildew, and Botrytis bunch rot.
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. A more 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.
Ph.D., Plant Pathology, University of California, Riverside, 1981
M.S., Wageningen University, The Netherlands, 1975
I contribute to outreach to grape growers (communicate research findings and general education on plant diseases and their management), and master gardener training.