First things first: I’m going off-line later today for a rare, two-week, no-work vacation. Please note that I won’t be responding to emails that come in during that time.
Veraison is on or near in Vermont vineyards, which signals the start of the ripening period. That means a few things:
1. Get your pest management in order. Diseases should be kept down to a dull roar by now, and grape berry moth or Japanese beetle treated. Your window to apply fungicides that may affect fermentation, especially captan or sulfur compounds, is closing. It’s been dry, so there shouldn’t be too much in the way of late-season diseases if you managed them well so far.
2. Finish your canopy management. Grapes need to see the sun from now through harvest, so make your final passes through to comb shoots and pull leaves where necessary.
3. Get rid of green fruit. At veraison, you can see where certain clusters from secondary buds r less vigorous shoots are behind the others. Drop those now, they will only drag down the ripeness of the others.
4. Get your nets, squawkers, scarecrows, and other bird measures ready, but wait as late as possible.
5. Collect petioles and send in for analysis to assess vine nutrient status. See this post for more details.
6. A couple of weeks before expected harvest, start assessing grapes for ripeness. Sampling should be methodical and regular (at least weekly, or more often as harvest approaches). Generally a 100 berry sample is sufficient to ascertain general ripeness.
Sugar level and pH are easily evaluated with simple tools (a refractometer and pH meter, respectively) available from most winemaking supply outlets. We recently published a fact sheet on Preharvest Winegrape Juice Testing.
Remember that for most popular cold climate grapes, TA is a primary determinant for ripeness; for reds (Frontenac, Marquette), a target TA of 1.5% or lower is preferred; for whites, 1.2% should be considered the upper end, although La Crescent may frequently have higher values. Ideally, all grapes for winemaking should have TA below 1%, but that is not always possible for the cultivars that we grow. Work with any wineries you plan to sell grapes to to determine their preferred juice chemistry levels before harvest.
Enjoy the end of summer, and good luck as you plan for what looks to be a great vintage.
Where trade names or commercial products are used for identification,
no discrimination is intended and no endorsement is implied.
Always read the label before using any pesticide.
The label is the legal document for the product use.
Disregard any information in this message if it is in conflict with the
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.