Workbook for Developing an Effective Fungicide Spray Program for Wine Grapes in Virginia
The purpose of this workbook is to help wine grape growers in Virginia develop an effective fungicide spray program for their production. The targeted diseases are: powdery mildew (PM), downy mildew (DM), black rot (BR), Botrytis bunch rot, and Phomopsis cane and leaf spot (Ph). Any of these diseases can be a significant threat to yield if an outbreak occurs. The proposed spray schedules intend to provide a simultaneous control of these five major grape diseases, and include several options that you could use as guidelines for your program. The workbook does not include all fungicides registered in Virginia for control of these grape diseases; thus, two supplemental tables are attached for your reference. Table 3 shows the effectiveness of fungicide you may select, and Table 4 lists fungicides that are prone to the development of fungicide-resistant pathogen isolates.
This information is merely suggested guidelines, and it is designed to serve as “food for thought”. There are many things to be considered beyond these guidelines, such as specific characteristics of your vineyards, varieties, training systems, diseases present in the field and their history, local weather patterns, your budget, etc. It is important to make sure that your program addresses these issues, and provides a good management of diseases while it fits your budget. Fungicide prices vary by year and location; thus, make sure to calculate cost per acre as you plan your program. The schedule I’m presenting here is based on commonly used fungicides such as mancozeb and sulfur products. It is simply because these products have lower risk of fungicide resistance development and generally cost less. However, I am not endorsing any particular products.