After a grapevine virus survey in Michigan, several economically important viruses were detected throughout the state with the potential to affect the production of quality grapes and wine. Growers and vineyard managers are advised to regularly scout vineyards for abnormal vine growth and make a yearly assessment of vineyard health and productivity.
MSU researchers say viral diseases can be difficult to diagnose based on symptoms alone. Some viral symptoms are mistakenly attributed to fall colors or confused with nutrient deficiencies. Viral symptoms also can vary greatly with the cultivar, especially when comparing red and white grapes and even within the season. In a single vine, mixed virus infections also can cause different symptom expression or symptomless infections can occur.
Possible problems with grapevine viruses in Michigan include the following:
• Viruses are difficult to diagnose in the field using symptoms alone.
• The effect of viruses vary across cultivar and growing seasons.
• No cure exists for infected grapevines, so limiting the spread of viruses and planting virus-free stock is critical.
Limited information is available as to how prevalent these viruses are in the state.
In the summer, Michigan State University Diagnostic Services will start offering molecular-based tests to check the health of grapevines. A team of specialists in plant pathology, nematology, entomology and weed science will work together to diagnose pest-related problems, providing a timely diagnosis of a problem and making appropriate recommendations of control.