June 9, 2014- At the UVM Hort Farm, we just entered into bloom on our earliest table grapes, and wine grapes are right around the corner. This immediate prebloom period is potentially the most important time to manage diseases in your vineyard this year. This is the time to get
Phomopsis, Black Rot, Powdery Mildew and Downy Mildew under control. This spray and the first post-bloom sprayare considered the most important sprays of the season for disease management.
Good spray options include a combination of a protectant (Captan, which may have a three-day re-entry interval depending on formulation, or mancozebs, whose 66-day preharvest interval make this likely the last time you’ll use them this season.) and systemic (QoI or DMI) fungicide. For DMI materials, Rally is the most commonly used fungicide, but there are several options for QoI materials,: Abound, Quadris (make sure neither of these contacts apples because they are phytotoxic to them), Flint, and Sovran. More details on appropriate fungicide
s can be found on pages 38 & 38 of the 2014 New York and Pennsylvania Pest Management Guidelines for Grapes.
As we get into bloom, vine nutrition becomes an important consideration. Grapes require boron and nitrogen to fertilize blossoms and form fruit, so this is a good time to apply both of those materials in your vineyard. Magnesium is also commonly deficient in Vermont vineyards, so consider applying either Sul-Po-Mag if you also need potassium, or Magnesium sulfate if you just need magnesium. This should be determined using both soil and petiole tests, and I can help you with interpretation of any results you have from the UVM or Dairy One (Cornell) labs.
Terence Bradshaw, UVM Tree Fruit and Viticulture Specialist
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The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM Grant, and USDA Risk Management Agency Funds.