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Corn+Soybean Digest

New Uses Review: Fruitful Research

Checkoff money invested in University of Tennessee research should soon bear fruit for U.S. soybean growers.

Pomologist Dennis Deyton and plant physiologist Carl Sams discovered that emulsified soybean oil controls mites and other pests on fruit trees, ornamentals and shrubs. It also delays bloom and thins fruit in peach orchards.

After seven years of research with promising results, the scientists are working with chemical company and soybean processing plant reps to jointly manufacture and market the new mixtures for fruit growers.

"We could have new products on the market as early as 2000 or 2001," says Deyton.

The potential payoff for soybean growers is significant. According to the United Soybean Board (USB), if the new products catch on, 25 million gallons of soybean oil could be used annually to delay fruit tree bloom. More than 15 million gallons could be used to battle insects; and 4.5 million gallons may be used to thin peach trees.

"Another thing that makes this research so rewarding is that it gives farmers the opportunity to use products made from soybeans, which are produced by farmers." So says Mark Eck, a Henderson, MD, farmer and vice chairman of USB's new uses committee.

In their research, Deyton and Sams learned that soybean oil can be used instead of petroleum oil to smother overwintering pests such as scale insects, aphids, two-spotted spider mites and Southern red mites.

Oils are attractive as insecticides and miticides. That's because they're the only widely used class of pesticides to which no species of insects or mites is known to have developed resistance. Mites are especially difficult to control, as they quickly develop resistance to synthetic miticides.

"In some cases, we saw better control with soybean oil and less phytotoxicity for some plant species. And beneficial insects, such as ladybugs, were not affected by the application," says Deyton.

The spray mix consists of water, an emulsifier and soybean oil. Dormant spray mixtures, applied between early February and late April, contain 3-4% soybean oil. Summer mixtures, applied in June and July, contain 1% soybean oil. The researchers spray 2-3 gallons of the mixture on each tree.

When the spray mixture is made with larger amounts of soybean oil, it's very effective at delaying bloom and thinning fruit in peach trees.

Fruit growers often seek to delay bud development on trees to escape early season frosts.

"With a soybean oil spray, we can see a delay of about six days," says Deyton.

Some buds die in the process, which thins the upcoming crop, bringing it to a manageable level.

"The soybean spray thins fruit on the trees more cost-effectively than hand thinning."

While most of the research has been with peach trees, Deyton says the soybean oil-based spray could also work on apple trees.

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