Evaluation of the Cultivar Effect on Wine Grape Fungal Diseases with a Use of a Low-Input Fungicide Regimen in Southeastern Virginia, USA

Wine grape cultivar selection was examined as a use of biotechnology and a part of integrated plant disease management in grape and wine production. The efficacy of 18 wine grape cultivars against various wine grape diseases was examined using a relatively low-input fungicide regimen to determine whether these diseases can be managed under hot and humid southeastern Virginia conditions over 5 years. Disease developments of black rot, Botrytis bunch rot, downy mildew, Phomopsis cane and leaf spot, and powdery mildew was evaluated. Although overall level of disease was low in each year, we observed a significant (P ≤ 0.05) effect of cultivar in many cases, indicating the importance of cultivar selection. Cultivars such as ‘Norton’, ‘Noire’, ‘Traminette’, ‘Vidal blanc’, and ‘Viognier’ were found to be less susceptible to the major diseases under Virginia environmental conditions.