Mr. Anti-Freeze

Alginate gel encapsulation cuts grape losses due to late frosts

All too often, warm, early spring weather lulls fruit trees into budding only to be blasted by a bitter frost that can kill an entire a summer's crop. Late frosts after bud break account for more than 40 percent of fruit crop losses in Colorado, making it fruit farmers' number one problem. If the buds would sleep for just a few more days or weeks, the crops might be saved.

Cecil Stushnoff, a Colorado Agricultural Experiment Station horticulturist, has found that buds on fruit trees and plants will stay dormant longer when encapsulated in alginate gel — the same stuff that's used for vitamin, herb, and medicine capsules. Stushnoff and viticulturist Rick Hamman apply alginate gel to buds in early spring to shelter them from cold weather and delay bud break by three to four weeks.

"This is pretty simple, available, and environmentally friendly," said Stushnoff. "When the buds are ready to bloom, they push through the gel."

Once in bloom, their development catches up with normal growth and crops are ready to harvest on schedule.

The soil and climate in western Colorado are perfect to raise high-quality grapes such as those grown in California and Europe for wine — except for occasional late frosts. Stushnoff's technique has been successful for three years in grape crops near Grand Junction. Researchers growing peaches in Georgia likely will use the technique this spring if early warm weather patterns are expected.

In Colorado, alginate gel can be sprayed on plants any time between mid-March and the second week of April. A hard rain, or lots of it, will wash the solution off, but in most cases, the treatment delays bud break in about 40 percent of the crop. Although some fruit may be lost to a late frost, the treatment helps prevent catastrophe.

Stushnoff and others have been unable to find any significant negative effects of the treatment. Fruit still has the same maturity date, yield, and quality.

"Our biggest question is, do you try to prevent something you aren't sure will happen? If there isn't a late frost, it's not economical to apply the gel," said Stushnoff. However, winter weather can be monitored closely, and if temperatures start to rise too early, the alginate gel encapsulation can be applied quickly and efficiently.

That, indeed, is part of the beauty of this technique. It's simple. It's effective. And, although cost analysis hasn't been conducted, it should be affordable.

Stushnoff stumbled upon the idea when looking for ways to freeze- dry plants to preserve them for genetic development. When water was extracted from plant samples, the samples could be cryo-preserved — or frozen — and kept in liquid nitrogen. Incredibly, many plants, once devoid of water, survive minus 321 degree Fahrenheit temperatures. Because water within plants freezes, extracting water from a plant drastically increases its resistance to cold. Stushnoff reasoned that if the effects of freezing can be manipulated so much in a laboratory, why not try to change the effect of cold weather on plants? Even a few degrees of temperature resistance can make the difference between a total crop loss and a productive season.

Stushnoff and other researchers continue to look for ways to make the gel more stable, give it more lasting- power in wet weather, and increase its effectiveness on the entire crop. By adding white latex paint to the formula, for example, they are able to delay bud break even more. The white color reflects sunlight, keeping the buds cooler in deceptively warm early-spring weather and giving Colorado fruits crops a better chance to survive late frosts.