Glyphosate-resistant weed among treated soybeans. Courtesy of Amit Jhala.

As more Nebraska soybean farmers have planted dicamba-tolerant seeds, the number of complaints about off-target injury has gone down.

“Every year now the production of Xtend soybeans is increasing and so do the use of dicamba-based herbicides,” said Amit Jhala, weed management specialist at the University of Nebraska-Lincoln.

Bayer’s Roundup Ready 2 Xtend soybeans are dicamba and glyphosate resistant. Producers can apply dicamba-based herbicides to kill weeds without damaging their crops.

After a series of federal court rulings this summer that put dicamba use in jeopardy, Nebraska soybean producers and commercial pesticide applicators are free to treat their dicamba-tolerant crops with three hotly disputed dicamba-based herbicides through July. A group of conservationists and farmers had sued the EPA over its 2018 re-registration of Bayer’s dicamba-based herbicide, Xtendimax, because the chemical has drifted into other fields causing damage to non-resistant crops.

According to a Ninth Circuit Court ruling in early June, from 2013 to 2015 herbicide drift complaints made with the EPA averaged around 1,000 annually, but after dicamba-tolerant seeds were introduced in 2016 that number began to rise. In 2017, complaints grew to more than 3,000, but in 2018 it decreased to around 2,250. At the same time, acres planted with dicamba-tolerant seed increased from 27 million to 56 million.

In Nebraska, the number of complaints received by Nebraska Extension for dicamba off-target damage increased from 259 in 2017 to 280 in 2018. That increase in complaints came as the number of acres planted of Roundup Ready 2 Xtend soybeans, Bayer’s dicamba and glyphosate tolerant soybean, increased from 500,000 to 3 million. In 2019, the number of complaints shrank to 185 as acres of Xtend soybeans increased to about 4 million, that comprised around 80% of the state’s genetically engineered soybeans.

october19 feature wechsler fig03 01 450px.png?v=5323 - The rise of dicamba soybeans in Nebraska

However, observed dicamba damages were not always reported. In a 2017 survey conducted in Nebraska by Weed Science Society of America, only 7% of respondents who noticed dicamba injury filed an official complaint.

Producers will have to consider new options for next year as the chemicals won’t be available come fall for discounts on early-purchase orders.

“I think producers will be looking at alternatives, whether it be alternatives that use dicamba as part of the program or alternatives that use other products,” said Steve Nelson, Nebraska Farm Bureau President. “Producers will look at all options.”

The federal court’s ruling found multiple instances of farmers feeling compelled to adopt dicamba-tolerant soybeans to avoid economic costs from damages.

The judicial opinion shows that in September of 2017 Rob Robinson, owner of Rob-See-Co seed company in Elkhorn, had written the EPA warning of reports of damage: “The amount of damage I am hearing about from my soybean seed customers and sales force is alarming. Even more alarming is the number of my customers who have told me they will plant all Xtend varieties, instead of my non-DT seed, as a defensive measure.”

Robinson found the injuries to be “anticompetitive.”

The court’s ruling last month ended the herbicides’ label registrations, effectively ending their continued sales in 2020. But, that decision did not go uncontested throughout June.

The initial ruling on June 3 that revoked the herbicides registration left farmers and commercial applicators in a legal gray area. The Nebraska Department of Agriculture decided to allow continued use of the dicamba herbicides pending orders from the EPA. That came days later when the EPA said that remaining supplies could be used through July.

In the middle of June, the court sided with the EPA, thus allowing dicamba herbicides to be used through July, a disappointment to plaintiffs who had pushed to have use halted immediately.

The court’s denial means the three herbicides are no longer available for purchase this year. Those registrations were set to expire in December. Bayer has already re-submitted Xtendimax for 2021.

The dicamba-tolerant seeds and over-the-top dicamba-based herbicides were created to address growing glyphosate resistance in weeds. With the growth of glyphosate use beginning in the late 90s, weed resistance has caught up. According to the International Herbicide-Resistant Weed Database, the number of glyphosate-resistant weeds stands at 50 globally.

The Xtend soybeans are resistant to glyphosate as well as dicamba, Jhala said. The seeds are genetically stacked with multiple herbicide-tolerant traits.

biotechcrops 450px.png?v=9402 - The rise of dicamba soybeans in Nebraska

There are six weed species with confirmed resistance to glyphosate in Nebraska; common and giant ragweed, kochia, palmer amaranth, marestail and common waterhemp.

With heavy reliance on a certain chemical, weeds adapt faster. Palmer amaranth has been registered as having dicamba resistance, and kochia in western Nebraska has shown a reduction in dicamba sensitivity.

“Glyphosate is still the number one most commonly used herbicide,” Jhala said.