—by Matt Milkovich

As winter warm-ups and cold snaps become more frequent and less predictable, grape growers need more accurate ways to predict bud cold hardiness in their vineyards, such as this research vineyard at the West Madison Agricultural Research Station in Verona, Wisconsin. University of Wisconsin-Madison and Cornell University researchers are developing an online tool that can estimate grapevine bud cold hardiness. (Courtesy Michael North/University of Wisconsin-Madison)
As winter warm-ups and cold snaps become more frequent and less predictable, grape growers need more accurate ways to predict bud cold hardiness in their vineyards, such as this research vineyard at the West Madison Agricultural Research Station in Verona, Wisconsin. University of Wisconsin-Madison and Cornell University researchers are developing an online tool that can estimate grapevine bud cold hardiness. (Courtesy Michael North/University of Wisconsin-Madison)

Winter warm-ups and cold snaps seem to be more frequent and less predictable, intensifying fears of annual vineyard losses. Researchers are developing new tools to deal with the new extremes.

Amaya Atucha
Amaya Atucha

University of Wisconsin-Madison associate professor Amaya Atucha leads one project, funded by $300,000 from the U.S. Department of Agriculture, to develop ColdSnap, an online tool for estimating bud cold hardiness. The tool will help growers to protect grapevines from winter injury and make site and cultivar selections. Atucha discussed the project during the Great Lakes Fruit, Vegetable and Farm Market EXPO in December. 

Atucha and UW-Madison collaborators Al Kovaleski and Michael North, as well as collaborators from Cornell University, have already developed cold-hardiness prediction models for common Vitis vinifera and cold-hardy hybrid cultivars. As part of the ColdSnap project, they’ll integrate the models into Cornell’s Network for Environment and Weather Applications (NEWA) system. 

Previously, there wasn’t an easy way for growers to access these cold-hardiness prediction models. Cornell senior extension associate Dan Olmstead is building a ColdSnap interface that will improve accessibility for anyone who uses NEWA, said Cornell associate professor and project participant Jason Londo. 

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The researchers plan to combine aspects of the other models into a single ColdSnap model that growers will be able to access via phone app or web browser. ColdSnap will display average cold hardiness by cultivar and location, and it will rate the probability of freeze damage as low, medium or high. It also will give general management recommendations, Atucha said.  They’re still testing the ColdSnap tool, but the beta version will be available in early 2025, she said. 

Washington State University’s AgWeatherNet system also hosts a cold-hardiness model for grape cultivars. While it does a good job predicting cold hardiness in Washington, it didn’t work as well in other regions because it was built on historic climate data for the Pacific Northwest, Atucha said. 

The Cornell and UW-Madison models are built on weather data from the Northeast and Midwest and include recently developed physiological cold-hardiness parameters that can increase prediction accuracy and allow the models to be extrapolated to other growing regions, she said. 

One approach to calculating cold hardiness is differential thermal analysis, which captures the release of energy from bud tissues at the precise temperature the bud freezes. The researchers based their model on the metric called LT50, the lethal temperature at which 50 percent of buds would freeze in the field, which can be used as a threshold to predict substantial vineyard damage, Atucha said. •