Earlier this summer, many growers, suppliers and educators figured the lessons learned the hard way in 2017 and 2018 would dramatically reduce this year’s concerns about dicamba use on soybeans.
But as it turns out, it didn’t happen, along with chemical company representatives this year spreading fictional stories about the cause of damage from this herbicide.
University of Illinois weed scientist Aaron Hager says several commercial retail applicators have indicated chemical company representatives are blaming dry weather stress, Liberty Link beans, ammonium sulfate (AMS) and tank contamination as major causes of soybean leaf cupping in order to cover up dicamba damage.
Hager believes soybean leaf-cupping damage is totally due to dicamba application. Since he hasn’t found any published scientific literature that indicates otherwise, he’s asked industry representatives to justify their damage theories.
Dry Weather Stress
With no research that describes how environmental conditions can induce soybean cupping, he’s asked the industry to explain how so-called environmental stress can induce widespread leaf cupping. He also questions how environmental stresses can start and stop at a property line and how dicamba-resistant varieties are somehow protected from this environmental stress.
In 25 years of evaluating soybean plots at the University of Illinois, Hager never recalls observing AMS causing leaf cupping symptoms similar to those caused by dicamba. While some folks are blaming AMS for cupping with Liberty Link soybeans, he questions why AMS wouldn’t also be causing similar symptoms with non-Liberty Link soybeans.
He adds that millions of Illinois soybean acres have been sprayed with glyphosate plus AMS since 1996 without the widespread leaf cupping that has shown up over the past 3 years.
While there were limited instances of cupping due to contaminated application equipment in 2017 and 2018, Hager thinks growers and ag retailers are doing a much better job of sprayer hygiene with EPA’s mandated dicamba education.
Hagar says seeing uniform soybean leaf cupping throughout fields isn’t suggestive of any of these causes. Instead, he’s convinced it’s totally due to exposure through volatility of previously-applied dicamba.
“Multiple university weed science programs have demonstrated volatility of the dicamba formulations can be detected for up to 4 days after application,” he says. “Yet these results seem to be largely ignored by industry as another possible source of exposure.”
The crop protection industry owes it to farmers to tell the truth and avoid dreaming up fictional stories about dicamba failures. Plus, there’s no need to add consumer concerns about the safety and role of ag chemicals in today’s food production.