Cold Protection Resources for Citrus Growers

Josh McGill freeze, Weather

Citrus growers in Florida’s Panhandle will have a greatly reduced citrus harvest this year because of a hard freeze in December 2022, the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) reported. To help growers reduce damage in future freezes, UF/IFAS has tools that aid with citrus cold protection.

cold protection
A citrus freeze occurred on Dec. 24, 2022, in North Florida.
(Photo by Daniel Williams, UF/IFAS)

Water is the most common form of cold protection in Florida. Growers using water must determine the minimum critical temperature of their citrus trees and then be equipped to operate their irrigation systems to prevent damage to the crop.

UF/IFAS Extension’s Florida Automated Weather Network (FAWN) has assembled a Cold Protection Toolkit containing six resources/tools that can be used in preparing for a freeze event. They allow growers to set their critical temperature for their trees to be used with the other resources in the toolkit. Growers who are unsure of their crop’s critical temperature can find more information here.

A FAWN Freeze Alert Tool in the toolkit allows growers to receive a text and/or email message when certain conditions occur at the FAWN station closest to them. There is also a National Weather Service tool that provides a graphical forecast for temperatures, wind and rainfall. There is an estimation tool for minimum overnight temperatures and a forecast tracker that shows how well the forecast is tracking the actual temperature.

The Evaporative Cooling Potential feature utilizes a table showing four categories of risk and criteria for each category. The user-supplied forecasted values of air temperature, wet bulb temperature and wind speed are used along with the table to determine if evaporative cooling is possible. If evaporation occurs from windy and dry conditions blowing over a wet plant surface, the plant’s surface temperatures can be lower than the actual air temperature. This is evaporative cooling, which can result in plant damage when the wet bulb temperatures lower past the critical temperature of the tree. Growers using irrigation on nights that the air temperature could be close to the critical temperature could experience more damage than if no action was taken. By utilizing the Evaporation Cooling Potential feature along with leaf freezing temperature data, citrus growers could potentially save money and water and reduce the risk of evaporative cooling damage.

The Wet-Bulb Based Irrigation Cutoff Temperature uses the current air temperature and the wet bulb temperature to calculate a “new” wet-bulb temperature at the critical temperature. The new wet bulb temperature is the temperature at which the irrigation system can be safely shut down.

Source: UF/IFAS

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