COLUMBUS, Ohio —After statewide bans, multiple lawsuits and countless disgruntled farmers nationwide, the U.S. Environmental Protection Agency has required the makers of dicamba, a controversial weed killer, to revise its label.
The label changes and new training requirements shift more responsibility into the hands of farmers to ensure if they apply dicamba, the herbicide does not spread to neighboring fields. The problem is the weed killer has been shown to easily go airborne and move far from its intended area, harming or killing plants and other crops along the way.
“You can do everything right on the day you apply it, then later that day or the next morning, it can still move,” said Mark Loux, an Ohio State University Extension weed specialist. OSU Extension is the outreach arm of the College of Food, Agricultural, and Environmental Sciences (CFAES) at The Ohio State University.
Dicamba is typically applied to eliminate weeds in fields of crops that are genetically modified to withstand dicamba such as some varieties of soybeans. The weed killer can kill broadleaf weeds, as opposed to grasses, and can harm or kill any crop that’s not genetically modified to tolerate it.
Beginning in 2018, farmers who apply dicamba to their fields will have more label restrictions on when, where and how they apply the weed killer, to try to keep it from turning into a vapor and spreading to plants it was not intended to reach. Monsanto, BASF and DuPont, the companies that make weed killers with dicamba, are revising their product labels to add various constraints including stating that only people certified to apply restricted-use pesticides can apply dicamba. Also, anyone applying dicamba must go through annual training specifically on dicamba. Currently, no training is needed to apply the product.
Though such measures are aimed at preventing the unwanted movement of dicamba, it is doubtful they will greatly reduce the possibility of unintended harm to plants nearby, Loux said. That’s because dicamba can be volatile, so it is difficult for an applicator to control where it might end up, he said.
“I think we’ll have more issues. That’s my prediction. We’re all sort of holding our breath,” Loux said.
Across the U.S. this year, millions of acres were unintentionally harmed or destroyed by dicamba. So much damage occurred in some states that it has been banned.
The most damage occurs when dicamba is applied to fields after crops have emerged from the ground, so it is safest to apply dicamba in early spring before the crops begin growing, Loux said.
Typically farm insurance policies will cover the damages of pesticide drift if it is caused by the applicator’s negligence such as a mistake in mixing or misjudging wind speeds, said Peggy Hall, agricultural and resource law field specialist for OSU Extension.
But insurance policies commonly exclude pesticide drift damages if the applicator failed to follow label instructions, she said.
“Then you’re in a difficult situation,” Hall said. “We have to raise the question as to whether we’re willing to take that risk of applying dicamba. I think that’s a valid question to be asking.”
The additional restrictions for farmers who apply weed killers containing dicamba in 2018 include the following:
- A buffer is required if wind is blowing towards a sensitive area. If the wind is blowing toward a sensitive crop, dicamba should not be applied.
- The maximum wind speed when dicamba can be applied is 10 m.p.h. It had been 15 m.p.h.
- Dicamba can only be applied between sunrise and sunset and never during a temperature inversion, which is when the air near the ground is cooler than the air above it. Under those conditions, the wet dicamba particles stay in the air and with wind, can drift off site. Between sunrise and sunset, temperature inversions are less common.
- Only those certified through the state or operating under the supervision of someone who is certified will be allowed to apply dicamba. Training for pesticide certification will now include information about dicamba use and applicators will be required to maintain records on the use of dicamba products.
For more information about using dicamba, visit: u.osu.edu/osuweeds/