Dicamba has been used for more than 50 years, mostly on corn and roadside projects. But there’s a concern this year that it’s having a big impact on Iowa crops.
“Since it’s introduction there have been situations with off target movement, but this year is by far the most severe it’s ever been,” says Bob Hartzler, Agronomy Professor at Iowa State University specializing in weeds. He says soybeans are sensitive to dicamba and the chemical can volatilize in the environment. That means applicators can do everything correctly in terms of keeping the product where its supposed to go, but still it can move around..
This is the fourth year of dicamba ready soybeans and there have been isolated cases of dicamba movements in the past causing lawsuits but this year is a different scenario.
Hartzler thinks a condition that comes from the volatile nature of dicamba called atmospheric loading is more prominent this year because of the weather. There hasn’t been much rainfall after peak application seaso. and rain helps disperse the chemical into soil where it is less likely to volatilize.
Another issue could be a quick planting season. With both corn and soybeans growing faster there were incidences of fields getting sprayed at the same time.
“Extension area agronomists, and also commercial agronomists out there, they’ll tell you that nearly every non-dicamba resistant soybean field is showing injury and in many, if not most of the fields. The injury is uniform from fence row to fence row and that’s just not what we’ve observed in the past,” Hartzler says.
Three registrations of dicamba have been revoked by the Ninth District Court which ruled with a coalition of environmental groups including the Center for Food Safety. The court says there was an absence of substantial evidence to support the EPA’s decision to register dicamba products. They say it failed two requirements: there was satisfactory data submitted and it will not significantly increase the risk of any unreasonable adverse effect on the environment..
The Environmental Protection Agency says farmers are allowed to spray those products until the end of July.