New model helps grape growers predict freeze damage

By Blake Jackson

Climate change is shortening winters and causing grapevines to bud earlier, making them more vulnerable to spring frosts. A new computer model developed by Cornell University can help grape growers in the Northeast predict freeze damage to their crops.

The web-based model allows users to select their location and grape variety. It then uses weather data from thousands of stations to estimate whether the buds have likely suffered freeze damage. This information is crucial because damaged buds won't produce grapes that season.

"If a freeze event occurs and surpasses a cultivar's tolerance, the bud dies, impacting the harvest," explains Jason Londo, a Cornell professor involved in the project.

Different grape varieties have varying levels of cold hardiness, which changes throughout winter. They are most tolerant in mid-winter but less so at the beginning and end of the season. While some hardy cultivars can withstand temperatures as low as -20°F in mid-winter, new spring growth is highly vulnerable to frost due to its higher water content.

Cornell researchers have been collecting data on grape cold hardiness since 2009. This data is used in the model, but it's specific to their location. The model allows users to input their local weather data to receive a prediction for their area.

"This model might not be as helpful in mild winters, but in the future, if we have a cold snap in March or April, growers can use it to see if it was cold enough to cause damage," says Londo.

If the model predicts damage, growers can assess the extent by examining buds with a razor blade. This information can then guide decisions such as adjusting pruning practices or seeking alternative fruit sources.

The Cornell team is continuing to monitor grape cold hardiness and collaborating with others to verify the model's effectiveness across different regions. They are also researching the genetics of cold hardiness and slower bud break as ways to mitigate the risks posed by a changing climate.

"As the climate warms, frost risk doesn't necessarily decrease," says Londo. "We're working to understand the effects of freeze damage and develop new technologies to help growers adapt to a more unpredictable climate."

Photo Credit: cornell-university