Who Burned the Beans?

Post-Herbicide Injury Up

Herbicide burn isn't pretty to look at, but most soybeans will recover. (DTN photo by Pamela Smith)

In the words of Yogi Berra, when it comes to postemergence soybean treatments, it's like deja vu all over again. University of Illinois weed scientist Aaron Hager expects many soybeans will likely feel the burn this summer as growers supplement glyphosate with contact herbicides.

"These things go in cycles. Growers rely on a single product until it breaks and then start adding other chemistries to the tank to address the problem that results. It's cause and effect. Farmers are now reaching back and using some of the chemistries they depended on in the 1980s before switching to Roundup," Hager said.

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"Given the problems glyphosate now has on the Amaranthus species [pigweeds such as waterhemp and Palmer amaranth], about the only option left in glyphosate-resistant varieties is diphenyl ether products [Cobra, Ultra Blazer, Flexstar, Reflex], and they are going to burn," he added.

On bright and sunny days, those herbicide injury symptoms can occur within a few hours. Reddish-colored spotting on the leaf surface may appear shortly after the herbicide is applied. Plant leaves can yellow and then turn brown and die. Crop oils and other additives, high humidity and environmental factors can increase plant injury.

The good news is soybeans are resilient, and a little burn isn't likely to do permanent damage. Products will differ in amount of burn, and even time of day can make a difference. Hager said it helps if growers understand those differences as they evaluate herbicides. He recommended a week or two of patience to see how the plant recovers. In the case of burnt soybeans, Berra would likely say: "It ain't over 'til it's over."

Pam Smith can be reached at pam.smith@dtn.com

Follow Pam Smith on Twitter @PamSmithDTN

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