Monitoring Grape Bud Hardiness in 2022-23

We are ramping up our annual bud hardiness monitoring project once again. The project is now being led by Jason Londo, fruit physiologist at Cornell AgriTech. Many of you have heard Jason speak at B.E.V. NY in the past about the recent development of new models that predict grapevine cold hardiness based on weather data. This year, we are beginning to see the results of that work by means of how this information is being presented to the industry on the project website. The landing page for the project looks very much the same as it has in the past, but when you click on the link for this year’s data, you’ll be met with something that looks very different than past years, but also very informative. It’s important to mention up front that this new site is still a work in progress, so it is still being worked on to sort out bugs and add more information over time.

2022-23 Low Temperature Exotherm Data (link)

The new site essentially has two parts. The first one is a broad, regionwide map showing estimated freezing tolerance (measured by LT₅₀, the temperature needed to kill 50% of buds in a sample) for several vinifera, hybrid and native varieties. These maps are based on the models that Jason and his lab have been developing for a number of years now, plus weather data from various weather stations across the region. You can see a map of either freeze tolerance or potential damage by cultivar, with color coding on the map based on the model’s output for those areas. Currently, the freeze tolerance scale stretches from a little above -20°C (-4°F) to almost -30°C (-22°F) (see Fig. 1).

The second part of the new site lets users drill down to more specific locations. Below the regional map, you’ll find a map of the Northeast with a lot of dots on it. Each dot represents a weather station that you can select to see what the predicted LT50 values are for each of those locations based on the models. The two sites with grape clusters represent Geneva and Portland, where measurements are currently being done to continue honing the models. The results of those measurements are shown for those two locations.

When you select a particular station, the windows below will show the measured low temperatures at that site, along with the predicted freezing tolerance for the chosen cultivar, which can be selected by the user. These graphs will look more familiar to those who have looked at these charts in previous years. In the case of Geneva (Fig. 3), the chart displays the LT₁₀, LT₅₀ and LT₉₀ values for each cultivar, along with the predicted LT₅₀ value from the model (the gray line). If you hover your cursor over each of the lines, it will show you the value for each time point that is charted. In this case, the measured LT₅₀ for Gewürztraminer as of last week is about -6.7°F, and the modeled LT₅₀ was -7.2°F.

Below that chart is a second one that predicts the amount of potential bud damage for that cultivar based on the weather to this point. The current chart shows 0% potential for injury because the low temperatures at Geneva have not reached the point where we would expect any damage. As with previous years, once the low temperatures start approaching or crossing the LT₁₀ or LT₅₀ lines, growers should be assessing damage in their own blocks.

The biggest advantage of having a model to predict freeze tolerance is that growers in all parts of New York and elsewhere can get an idea of how much potential bud damage there might be in their own area, not just where we are sampling.

I encourage growers to check out the new site and see how it works for themselves. As I mentioned, it’s still a work in progress but it provides important information about potential bud injury for growers around the state, not just a few locations in the Finger Lakes and Lake Erie regions.