As she had last year, Dr. Katie Gold, plant pathologist at Cornell, has posted a summary of grape disease issues and recommendations. Here it is as a web page and as a PDF.

Growth in the UVM vineyard ranges from bud burst to 2-3 shoots emerged; a few shoots are nearing three inches in length. It’s time to really be thinking about protecting vines from early season disease infections. Most cold-climate cultivars will not need disease protection until 5-8” of shoot growth, but any vineyards with heavy disease pressure last year and organic vineyards may wish to begin earlier, especially if inoculum reduction through thorough removal of diseased wood and mummy berries and/or dormant application of lime sulfur was not performed. I still recommend our fact sheet, An Initial Integrated Pest Management (IPM) Strategy for New Cold Climate Winegrape Growers as the best resource to boil the decisions down to a simple ‘prescription’, with the caveat that since it was written some new pest management materials have been released and inoculum may have increased in your vineyards which could lead to increased disease pressure. Growers should have an up-to-date copy of the New England Small Fruit Management Guide (on-line and hard copy versions) and/or New York and Pennsylvania Pest Management Guidelines for Grapes as a reference for specific materials, their efficacy, and use considerations. Remember however that the guidelines are written largely for vinifera and less disease-resistant hybrids, so the specific spray programs recommended may be overkill in Vermont vineyards.

I’d say any time now is good to get your shoots thinned down to 3-5 shoots per foot of canopy. Keep more on more vigorous vines, less on weaker ones.

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