Out with the Old, In with the Older

by: Samantha Teten, University of Nebraska-Lincoln, Agronomy Major / Agribusiness Minor

This blog is part of The Science Behind Dicamba Series from Dr. Andrea Basche’s course.

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My dad inspecting one of our soybean fields. Smart management of herbicides is important to my family and impacts everyone in NE Photo Credit: Melody Teten

As a person drives past the corn and soybean fields across Nebraska, it is fascinating to see how the crops grown and develop throughout the season. This past summer, the soybean fields looked a little different with the cupped soybean leaves and stunted growth. The culprit was dicamba herbicide; an old chemistry of herbicide with a new formulation and crop this year. Dicamba is a herbicide that targets broadleaf plants, and allows grass plants to live. The chemistry triggers the plant to grow excessively and abnormally to the point were the plant can no longer sustain its own growth, leading to death. Dicamba can be found in over one thousand United States products. So besides the average farmer with stunted soybeans, what does this mean for all of the other Nebraska residents? The dicamba controversy is bigger than just cupped leaves for a neighbor or even yield loss; this affects all consumers and the state of our economy. Soybeans were Nebraska’s second largest harvest crop in 2017 coming in at 5.7 million acres planted and nearly $3 billion dollars in value. Nebraska is also the 5th largest producer of soybeans in the U.S., providing a food source for livestock and poultry as well as soybean oil for human food products and renewable fuel. The value to our state’s economy makes it a concern for everyone in addition to the health concerns of dicamba sprayer practices.

Dicamba herbicide is not a new technology. It has been applied to corn acres for the past five decades, but in 2017, the first dicamba tolerant soybeans were planted widely. These genetically modified soybeans were planted to over 500,000 acres in Nebraska alone. In 2017, XtendiMax, Engenia, and FeXapan, the trade names of dicamba, were approved to be applied on soybeans. These formulations have reduced the volatility of dicamba, so the droplets and herbicide gas vapors are less likely to travel to the neighbors’ fields. However, a conflict arises because dicamba still moves away from the target more than it should, creating damage to soybeans without the trait and to vegetable crops. The quick adoption of these genetic and chemistry technologies of dicamba is because the timing could not have been better. Farm producers across the United States had become reliant on glyphosate with Round-up Ready genetics in both corn and soybeans, but that product is reaching the end of its life cycle with resistant weeds making glyphosate inactive. Dicamba is now an option to overcome this emerging challenge. It is a wonderful tool, but just as we can’t expect a hammer to fix all home repairs, we can’t expect dicamba to be the catch-all solution to weed challenges. In addition to the drift concerns, this old chemical has the potential to become inactive as well if resistance develops in weeds just as it did for glyphosate.

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Soybeans with cupped leaves. This is one of the indicators of dicamba damage to non-tolerant soybeans. Photo credit: Kelby Grint

Acres planted to Xtend soybeans are only expected to increase significantly in 2018 in both Nebraska and the United States. Precautions are being made to reduce the effects and claims made in 2017. It was estimated that over 50,000 acres of non-tolerant soybeans were injured with this herbicide and also vegetable crops across the state. Dicamba products have also been labeled as Restricted Use Pesticide. As a part of this, all applicators of dicamba will be attending a mandatory Auxin Herbicide Training to learn about the conditions and preventative actions to control the off-target effects. Late applications were more likely to cause injury to surrounding areas. Many labels and regulations are requiring applications to be complete prior to a specific date.

For more information on dicamba and the new actions for 2018,  check out Nebraska’s Department of Agriculture at http://www.nda.nebraska.gov/pesticide/dicamba.html or UNL CropWatch at https://cropwatch.unl.edu/2018/can-we-manage-dicamba-applications-2018.



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