Predictive model testing for downy mildew of Vitis vinifera (European wine grapes) in Georgia and timely use

Summary

A downy mildew predictive model was tested for Vitis vinifera wine grape production. The model accurately warned producers when downy mildew would initiate; due to accurately timed fungicide applications, producers were able to avoid catastrophic losses.

Situation

Wine grapes have been planted for some time in the Southeast, but the industry is expanding into new areas. Georgia's industry is smaller and newer compared to many other East-coast states (>20 wineries with sales of >50,000 cases per year), but a recent study by the Carl Vinson Institute (Univ. of Georgia) predicted over $585 million in business revenues from the winery industry over the next 20 years. The tourism that Georgia vineyards generate is equally or more important than the wine itself. As common weekend excursion destinations, wineries usually have tasting rooms, villas, restaurants, and they often entertain weddings. Due to a wet climate, downy mildew is a major disease of wine grapes in Georgia. On multiple occasions, wine grape producers have had 100% defoliation of vines due to this disease, resulting in winter kill and poor return bloom the following year. In some cases, the fruit actually rot from the mildew, resulting in poor quality grapes for wine production. Though producers are fully aware of the disease, and though fungicidal controls are available, producers often are not aware when environmental conditions will trigger an outbreak of downy mildew.

Response

Through collaborations with Italian scientists, a downy mildew predictive model (developed in Italy) was tested for the last two years (2011 and 2012). Warnings provided during the testing phase allowed producers to adjust their fungicide programs, resulting in significantly less disease pressure and losses due to downy mildew.

Impact

The information derived from the testing of downy mildew predictive models has allowed growers to both identify and respond to this imminent threat. As such, downy mildew was virtually nonexistent in vineyards that responded to the warnings, despite ideal environmental conditions for disease development. This resulted in higher-quality grapes that were utilized for higher-quality wines. Downy mildew can also result in defoliation, and this leads to unhealthy vines and winter kill; the reduction in downy mildew due to the use of these predictive models will result in better long-term health and survival of Vitis vinifera grape vines in Georgia.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2012
• Geographic Scope: Multi-State/Regional
• County: Lumpkin
• Program Areas:
  • Agriculture & Natural Resources