Managing Herbicide Drift in Soybeans

Farmers know that cupping of leaves in soybeans is often a sign of off-target spray applications, or herbicide drift, but what can you do to help the plant recover? Dr. Jim Smart, an agronomist with Ag Spectrum, says foliar nutrition can help, but it also must be applied at the right time and in the right conditions. Smart says he’s seeing more issues with off-target herbicide applications this year.

“This year, perhaps more than in the past, I’ve seen many examples of leaf cupping and strapping and deformed trifoliates on soybeans. It’s not just one area, I’ve seen this in Southern Illinois and central Illinois, Iowa, Missouri, Kansas, and even in Tennessee So, it’s not one isolated case, it seems to be quite widespread.”

Smart explains how off-target herbicide applications affect soybean plants and what farmers will see if it’s happened in their field.

“Some of the damage is very light and it’s just on the very tops of the plants, and so if it’s a very small dose, maybe it doesn’t affect the plants too badly. But many of the fields we’ve seen, it stopped, or nearly stopped root growth as well as shoot growth and leaf growth, and the leaves that do start coming out are all twisted and curled. And especially if the plants are already starting to set flower buds, the flowers are malformed, and I’ve even seen pods starting to develop that look like bananas shape where they’re curled and the beans inside them are flat instead of round, so that could be very detrimental to yield.”

Many farmers when they see damage want to do anything they can to help their field and Smart says one method is providing foliar nutrition, but farmers need to wait before doing so.

“If there are toxic pesticides on the plant, we need to give the plant time to metabolize or volatilized or otherwise break down, because if we try to stimulate growth of the plant and it’s already got a growth regulator on it that has goofed up the hormones in the plant, we may actually cause more damage to the plant, rather than helping it. So, we need to give the plants a couple of weeks to let that herbicide break down and then foliar nutrition may be helpful if it’s a very small dosage, and it occurred early in the life of the plant. If the plants were already flowering, most of the time, the flowers and flower buds that are present when that herbicide damage occurs, are nonproductive”

Smart says herbicide drift is impacting several types of soybean traits.

“This is not just affecting one trait I’ve seen it affect LibertyLink soybeans, Roundup Ready soybeans, Enlist soybeans, conventional soybeans. So, it’s not just one type or one area, it’s many areas and many different traits of soybeans are adversely affected by pesticide off target drift.”

To help prevent off-target applications, Smart says it’s important that applicators properly clean their spray tanks.

“We know that some of the growth regulators like dicamba or 2-4D have a greasy sticky film that will cling to the inside of tanks or rubber hoses, screens, lines, filters, and you can’t remove that by simply washing it out with water. It takes a clean agent to get that out of the lines, screens, filters, and pumps. And if you happen to have a poly spray tank it’s even worse because those chemicals can absorb into the poly plastic. So, a stainless-steel tank is preferred because they’re easier to clean and chemicals don’t absorb into the tank itself.”

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