Our Chardonnay and some of the hybrid vines are in bud swell stage as of this week, and others are tagging along. It looks like we will see bud break very soon with warmer temperature (but next week should be cooler). One of the diseases you need to consider this time of the year is Phomopsis cane and leaf spot. It causes minor leaf spots, which is more obvious to our eyes, but the more important damage is caused by necrotic lesions on shoots and rachis. It also causes berry rot; however, it is not common with wine grapes because of our spray programs. Materials for black rot and downy mildew are often effective against Phomopsis. Thus, the fungicide coverage for these diseases is also working as management of Phomopsis, especially later in the spring and early summer. Some cultivars, such as Viognier and Seyval Blanc, are more susceptible to Phomopsis than the others. Phomopsis takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become ...
Grape Disease Management Tips from Mizuho Nita (Grape Pathologist at Virginia Tech)