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Sprayable Frost Protection may Revolutionize Fruit Industry

By René Featherstone Western Correspondent

They call it “The Box,” and that’s just what it is, five-feet square, four high, its sides and the top door thicker than the steel because of insulation. A couple of thermometers lie on the bottom where deeply refrigerated air is pumped into the box that also contains fruit tree cuttings. It’s 24 degrees and dropping. The silky-soft, oh-so-tender fruit buds on the cuttings can’t be happy in this freeze chamber. How much cold can they withstand? That’s what he’s going to find out, said Mark Groszhans, orchard manager and field rep for Inland-Joseph, Wapato, Wash. Normally, ascertaining the critical temperatures of specific fruit varieties at specific stages of bloom is part of the company’s grower service, Inland-Joseph being one of only a handful of Washington warehouses that offer such freeze testing, Groszhans explained. Growers use the information from the freeze tests to implement frost protection measures and to adjust their blossom thinning rates. Today, however, the buds in the freeze chamber will yield data not directly for growers but for private researchers in Yakima. These test buds are on Robata apricot cuttings from the experimental plot in the orchard Groszhans manages out by Wapato; the plot had been treated with a new spray material that may revolutionize the soft fruit and apple industries in the Northwest – it’s a sprayable organic frost protectant, he said. Of all the weather, low temperatures are enemy number one as far as tree fruit farmers are concerned, Groszhans related. Winter freeze in the extreme can wipe out orchards by killing the whole trees; severe freezes can cause crop loss if the fruit buds sustain damage. Later, as the trees come out of dormancy and the buds start swelling and then blossom and then form the tiny green fruit at petal fall, frost can nip the crop in the bud, literally. Many millions of dollars are spent every year on freeze and frost protection in Washington state, even in years that are fairly normal temperature-wise. Conventional frost protection practices include running irrigation sprinklers and windmachines, and lighting return stack heaters or propane heaters that often are placed on the perimeter of blocks and then are referred to as border heaters. “Forty return stack heaters per acre is generally considered effective,” Groszhans elaborated. “Farm diesel right now is around $1.50 a gallon, so using smudgepots for frost control costs the grower in the neighborhood of $50 an hour, per acre. With a windmachine the up-front cost is about $15,000; a windmachine uses about seven gallons of gas an hour and it’s effective in raising the temperature two to three degrees on about 10 acres.” Noting that he gives horticultural advice to 80 orchardists in the Yakima Valley, Groszhans remarked that “just about all growers have windmachines that they supplement either with water or with heaters, or with both.” Typically they protect primarily their frost-prone blocks that usually are in low-lying areas because frost pools a lot like water does. “It’s not uncommon for a grower to spend thousands in just one night on heating an orchard when it gets really cold.” In the tests the freeze chamber temperature gets lowered in two-degree increments. Each batch of bloom is assayed after the cuttings have been removed from The Box and have warmed back up to above freezing. The actual damage assessment is ever so tedious, he noted, because each little blossom gets cut with a razor blade so the tiny pistil can be inspected. “If the pistil has turned from green to brown it’s damaged.” A sprayable frost protectant would be an asset for the fruit industry, especially in drought years when growers may not be able to use water other than for irrigation. “So far the tests have shown that this stuff works, although not as winter protection, and not on pears. I think we’ll need further testing to know more about the longevity of the product, and to be sure it does not have adverse effects on return bloom,” he said. Doug Anyan has been the project leader for developing the spray already trade-named Frost Bloc. Anyan works for the R&D firm Genesis Agri-Products, Inc, a subsidiary of G.S. Long Company, Inc, a Yakima ag supply firm. It’s quite the story how a new raw material was discovered in Hungary, he related. Reports of a creek not freezing over led Hungarian scientists to an ethanol plant. “It turned out that a byproduct of ethanol production was the cause,” Anyan said. It wasn’t long before industrial uses were found for the goo. “As road de-icer material, one gallon of the ethanol byproduct is equivalent to 50 pounds of salt.” At Genesis they experimented with it for a frost spray, Anyan said. “We got protection down to 28 to 26 degrees F, depending on the stage of bloom development.” However, the trials also showed that the de-icer sludge would ultimately not be practical for orchard use. For one, Anyan found that “the optimal rate was 20 gallons of product in 200 gallons of water, per acre,” which he felt was too high of a use rate. Secondly, “the batches really varied, they were not consistent.” It was obvious that manufacturers of road de-icer do not implement “the quality control we need for orchard materials.” Then Anyan started a search for “other products for our purpose that would do the same thing but at a lower use rate,” and found that the Canadian military was looking for an airplane de-icer that would be an ecologically sound alternative to the airplane de-icers commonly used. The disposal of toxic airplane de-icers, Anyan said, “is a major headache. It’s virtually impossible to contain them. A 747 requires a 1,000-gallon treatment for de-icing.” Enter an East Coast company that’s “basically a think tank for scientists,” who arrived at an airplane de-icer formula that’s “food grade, low volume, and biodegradable,” Anyan said. After Genesis entered into a secrecy agreement with the East Coast company, the scientists there tweaked the airplane de-icer formula in various ways to suit orchard use. Last year Genesis conducted four-tree replicated trials with altogether seven experimental Frost Bloc formulations, Anyan noted. The frost protection by Frost Bloc worked very well down to about 28degrees. After that, the frost kill ratio rose. But, Anyan emphasized, they took into consideration that an apple blossom survival rate of 20% is still regarded as a viable crop. Using that 20% as a marker, the tests showed that some of the seven Frost Bloc materials were effective down to 26 degrees and even slightly lower than that. “But there’s a limit to protection. Down at around 22 degrees there is no protection at all.” In the apple trials Anyan observed a side effect that points to potential hort benefits. “We noticed that the leaves also seemed to be protected down to 26degrees.” They did not analyze that effect on leaves, but he believes it’s worth looking into, he said. In fact, a series of upcoming on-farm trials will evaluate Frost Bloc efficacy on row crops including tomatoes, strawberries, lettuce, and sugar beets. Their 2000 trials also put the longevity of the seven formulas to the test. Indications are that Frost Bloc provides protection on the tree for at least two weeks after application, Anyan found. Regarding rates, he ascertained that the low volume aspect was indeed pertinent. “Doubling the rate did not increase protection.” Despite the fact that there’s still fine-tuning to be done, Genesis had hoped to have the Frost Bloc registered with the EPA before frost season this spring and begin marketing the product commercially. But that agency did not respond in a timely manner, probably due to the change in White House administrations, Anyan remarked. The research continues on a larger scale this year, involving scientists from the Washington Tree Fruit Research Commission (WTFRC). WTFRC director, Jim McFerson, called the potential of Frost Bloc “tremendously exciting.” “Not one grower who we’d asked to be a cooperator turned us down,” he said. In a broader context Anyan said that it’s not by chance that Genesis research focuses on developing chemistries that can be used in organic farming. “It’s a perception thing. When the consumer realizes that, ‘oh, it’s got organic registration,’ it’s good for everybody because it makes the fruit industry look green.” Groszhans said he was not surprised to hear that something as far-fetched as airplane de-icer might have an orchard use.