Getting — and staying — ahead of powdery mildew doesn’t happen by accident. Instead, success requires a consistent, well-developed, season-long management plan. While the exact steps and timing of actions may vary by vineyard and area, the best plans have the following components in common.
1. Understand the disease. Knowing how powdery mildew behaves under various conditions is key to controlling the disease. This model from the University of California offers insight into how to improve management decisions based on the pathogen life cycle and how it reacts to environmental situations.
2. Choose your chemistry class. The three most commonly used fungicides used in grapes include sterol inhibitors, like Viticure® fungicide, that inhibit the development of cell walls in the target organism, strobilurins and inorganics. Strobilurins interfere with energy production and cell respiration to prevent spore germination in fungi and inhibit mitochondrial electron transport. Inorganic compounds prevent fungi from attaching to plant surfaces.
3. Avoid resistance. You must rotate product chemistries during the season to prevent resistance and ensure long-term efficacy of powdery mildew fungicides. Avoid back-to-back applications of the same class of chemistry. Viticure has an advantage in that it is an imidazole which means it is not cross resistant to most other sterol inhibitors, and therefore aids in resistance management. Keep in mind that rotation brings out the benefits of each chemical group to deliver effective disease control while managing resistance development.
4. Follow the label. As with any control product, fungicides are most effective when applied at labeled rates and directed spray intervals. Therefore, don’t skimp on applications or extend timing of sprays. Also be sure to get good spray coverage during applications by practicing proper equipment maintenance.
5. Obey the weather. Use weather forecasts to help determine the best application times and to identify times of potentially higher disease pressure. Websites like this weather index can help.
Be sure to visit with your PCA or Chemtura AgroSolutions representative for additional ways to enhance your control program and ensure a successful season:
• Mike Ansolabehere, Southern San Joaquin Valley: (661) 304-3023 or email
• Matt Loftus, Central San Joaquin Valley: (559) 960-1112 or email
• Eric Leer, North Central California: (209) 531-6478 or email