Small soybean plants in field
UNUSUAL GROWTH: A trained agronomist will spot unusual growth patterns like these side-by-side plants display. Figuring out the cause can be difficult.

Determining cause of unusual leaf growth can be difficult

Soybean Watch: Herbicide injury could be involved in some cases.

Walking soybean fields is something Steve Gauck, Greensburg, Ind., does for a living. He walks his own fields as a farmer, and he walks customers’ fields as a sales agronomist for Beck’s. This year he’s walking a field in central Indiana designated as the Soybean Watch ’17 field. Beck’s sponsors the project.

Earlier in the season, Gauck noticed a couple of plants in the Soybean Watch ’17 field with unusual leaf growth patterns. One set of leaves on both plants were somewhat elongated and crinkled. “At the time I figured it was just a freakish growth symptom,” Gauck says. “You will find some of those now and then, and they usually don’t signify anything important.”

2 plus 2
Later Gauck received a few calls from farmers who had noticed similar distorted leaves on a few plants in their fields. That led him to research whether there was a possible common denominator causing what he and others were seeing.

Gauck now believes what he and other farmers saw may have resulted from a reaction to a Group 15 herbicide applied as a residual. Included in Group 15 are Zidua, Dual II, Magnum, Outlook and others. The Soybean Watch ’17 farmer applied Ledger. One component of Ledger is a Group 15 herbicide.

“The damage caused by the Group 15 herbicide in Ledger is very minimal,” Gauck says. “This kind of injury only happens in cool, wet springs like this one. Soybeans were growing slow enough that they don’t quickly metabolize the herbicide.”

People are paying more attention in some areas because of talk about dicamba drift, and this symptom can be confused with dicamba drift, Gauck notes. Group 15 herbicide damage will create a drawstring effect in the end of the leaf, causing it to turn down slightly.

Negligible effect
Overall, damage from Group 15 herbicides based on what Gauck has heard this year has been very small. However, he suspects many people have never seen Group 15 injury because they haven’t looked as closely in the past.

The same weather conditions that allowed slugs to hang around in many fields, including the Soybean Watch ’17 field, until almost July are the same conditions that allowed mild symptoms of Group 15 herbicide damage to appear, he believes.

When trying to determine if what you’ve seen is freakish growth or something such as herbicide injury, look for a pattern, Gauck says. Herbicide injury will likely have a pattern. It will follow a sprayer. You may find skips in symptoms, or it may be isolated to lower, wet areas or high, dry areas. In the Soybean Watch ’17 field, suspect plants were found in the lowest area of the field. “If it’s just a random plant here and there, it could be freakish growth,” he says.

Where there was minimal injury from Group 15 herbicides, Gauck doesn’t expect any yield damage. That assumes the injury occurred before the R1, or flowering, stage, which it did, in this case. It also assumes that new growth appeared normal.

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