Cornell University Viticulture Extension Specialist Hans Walter-Peterson had a message for Northeast wine grape growers who awoke to a snowfall Wednesday morning: Keep a close eye on temperatures, as vines can be vulnerable to a freeze following several days of warm weather.
Here’s the message Walter-Peterson, who is with the Finger Lakes Grape Program in Penn Yan, NY, issued Wednesday.
“I’m guessing many of you who are in the Finger Lakes are looking outside this morning (Wednesday, April 21) and watching the snow falling. Probably more concerning, though, are the temperatures that are being forecast for tonight in many parts of the region. Several forecasts that I’ve been looking at today are calling for temperatures to fall below freezing tonight.
“Normally this wouldn’t be much of a concern at this time of year, but after a series of warm, sunny days over the past couple of weeks, many of our varieties are at various stages of emerging from dormancy. At the Teaching Vineyard, our earliest varieties – ‘Jupiter’, ‘Marquette’, and ‘Marquis’ – are at or very close to bud-break. ‘Concord’ blocks were anywhere from bud-swell to starting to show pink late last week, which is further along than the buds were last year when a number of vineyards got frost damage. ‘Riesling’ blocks on Seneca Lake were also showing signs of life earlier this week, with bud scales being shed.
“Along with the colder temperatures, the forecasts are calling for winds to be in the 10-15 mph range tonight, which is more than enough air movement to eliminate any stratification of colder and warmer air that wind machines could help with. Jim Willwerth, a colleague from Brock University in Ontario, told me that any winds over about 7 km/hr (about 4.5 mph) virtually eliminate inversions, which would make wind machines ineffective. Winds over 13 km/hr (8 mph) can damage the blades of the machine, so growers with machines should pay close attention to wind speeds if they are considering firing them up tonight.
“There is still research being done to look into other methods to protect vines from frost damage, but there is nothing that has been shown to work consistently that I would recommend applying today that could protect against injury in less than 24 hours. At this point, we just have to wait and see what Mother Nature will bring.
“The two recommendations I can make once the temperatures warm back up again are:
- Evaluate damage and potential crop loss: You can do this by cutting buds to evaluate the extent of the injury if the vines have enough buds that you could afford to do so. The other option would be to wait until clusters begin to emerge when shoots grow to about 3-5” and count clusters. This can provide some sense of the extent of crop loss.
- Contact your crop insurance agent to start the claim process if you believe you will have a crop loss this season. It is much easier for them to close a claim if there is no need, rather than start one well after the event that caused the loss. Hopefully, nobody will have to do this, but it’s events like this that point out the importance of having some form of crop insurance policy for your farm.
“We will be trying to assess how much damage we see out of this over the next couple of weeks, but for now, let’s all cross our fingers and toes that we pass through this relatively unscathed.”