Yesterday's storm brought more than 2-inches of rain, and resulted in approximately 12.5 hours of wetness with an average temperature of 69F. It was an infection event for downy mildew and Botrytis (and Phomopsis and black rot, but they are less important at this time of the season, unless you have on-going Phomopsis issue). The other thing yesterday's storm brought was hails. We saw a minor, but obvious damages from the hail. Often time you will see random holes on leaves, clacks on berries, and sometimes, necrotic scars on canes. Please see the pictures below. The question is what will be the consequence of these wounds on berries. It depends on a few factors. If we have a nice hot day like today, these damaged berries more likely to be dried out; however, if we have another prolonged rain event, it can introduce Botrytis and other late season rots. It may also depends on how much sugar is available on these berries. The more su...
Grape Disease Management Tips from Mizuho Nita (Grape Pathologist at Virginia Tech)