June 7, 2020
First, sorry about lumping the grape growers in with my last apple email. I do know that you’re (mostly) separate entities with separate needs. That said, the importance of staying on top of disease management now is just as much there. We’re entering the critical immediate prebloom period in vineyards, when they are susceptible to pretty much all of the major diseases we face: black rot, Phomopsis. Powdery mildew, and early downy mildew. For non-organic growers, and combination of a protectant (captan or mancozeb) and a systemic / ‘kickback’ active material like a strobilurin, DMI, or SDHI would be warranted now and in the next application 7-10 days fr4om now. Be sure, especially with that latter group of materials, to rotate fungicide resistance classes so that you’re not using any class (e.g., 3 for DMIs, 7 for SDHIs, and 11 for strobilurins) more than twice back-to back. Some materials have more restrictive seasonal application caps- always check your label. For organic growers, I would recommend rotating copper and Serenade or bicarbonate (like Armicarb O or equivalent) on a fairly tight 5-7 day schedule. Then again, the dry weather has been nice for managing diseases. Organic growers need to really pay attention to sanitation and removed any diseased tissue as soon as it’s seen, and scouting should be done weekly.
I saw a good bit of grape tumid gallmaker in our UVM vineyard last week, enough that we treated for it. Usually, this insect is a curiosity, but we have seen and had others report that losses can be as high as 50% of fruit clusters ruined by the insect. Keep an eye out for it (pictures in the link posted) and consider treatment if more than 5% of fruit clusters or 15% of leaves are affected. Organic growers will need to crush galls by hand, non-organic can treat with Movento or Assail.
Get your shoots thinned. This will make life so much easier later this summer.