Jan 3, 2025

Fresh Views: Innovative freeze protection strategies for fruit crops

When colder weather sets in, fruit growers begin worrying about spring freezes. The questions surface quickly: Will the cold last long enough? Will a late freeze hit during bloom? Can we protect the crop — or will we suffer devastating losses?

For perennial fruit growers, especially in regions like the southeastern U.S. where temperatures can swing sharply, freeze protection is more than a concern. It’s a necessity. Various methods have evolved over the years, with different levels of success.

Traditional approaches to freeze protection

Early freeze protection methods relied on smudge pots, oil-burning heaters scattered through fields to raise air temperature. While they worked, pollution concerns forced their decline.

Other growers turned to tarps and physical covers to block frost, but these worked best on small plants, not large orchards. Fogging systems, designed to hold soil heat close to plants, proved unreliable under windy conditions.

Hoop houses offered consistent production and even heating options, but their high establishment costs limited widespread adoption.

Current tools: Irrigation and wind machines

Today, two methods dominate freeze protection in fruit crops: overhead irrigation and wind machines.

• Overhead irrigation starts before freezing temperatures arrive and continues until they pass. As water freezes, it releases heat, keeping flowers and fruit safe. But under low water pressure or strong winds, the system falters.
• Wind machines mix warmer air from above with colder air near the ground. This works well during temperature inversions, but proves ineffective in other freeze scenarios.

Both methods provide only a few degrees of added protection and require significant investment.

Nanocellulose: An emerging freeze protection strategy

Researchers are now testing nanocellulose sprays as a potential breakthrough in freeze protection. Derived from plant-based cellulose, nanocellulose is natural and biodegradable. When sprayed on crops before a freeze, the material forms a thin, insulating layer—much like a winter coat—that slows heat transfer.

Washington State University trials show nanocellulose sprays improve cold hardiness in grapes and sweet cherries by 3.6°F to 7.2°F. If effective on other fruit crops, this innovation could provide growers with a cost-effective and sustainable option.

Research at the University of Georgia

Since 2021, the University of Georgia has studied nanocellulose sprays on blueberries and peaches. Researchers tested different compounds, concentrations, and application methods across multiple bud stages.

Findings suggest some compounds protect early floral buds, while later stages show greater vulnerability. Critical questions still need answers before adoption:

• Which compounds provide the best protection?
• When should growers spray before a freeze event?
• How long does protection last?
• What temperatures can the sprays withstand?

While it’s too early to recommend nanocellulose for field use, research continues to refine how this technology may fit into future freeze protection strategies.

Looking ahead

Freeze protection remains one of the greatest challenges for fruit crop growers. Existing tools help but come with limitations and high costs. Nanocellulose sprays offer hope for a new, more sustainable layer of protection against unpredictable spring freezes.

With continued research and development, growers may soon have another reliable tool to safeguard their crops, reduce losses, and ensure strong harvests for years to come.

— Rachel Itle, Ph.D., is an assistant research scientist in fruit production and genetics in the Department of Horticulture at the University of Georgia. She is also a member of the Fruit & Vegetable 40 Under Forty Class of 2023. Itle’s research and Extension program focuses on perennial fruit crops, such as blueberries, concentrating on physicochemical fruit quality traits and their genetics. Her program also researches freeze protection and biostimulant applications.