CHICAGO (Reuters) – An Arkansas task force has advised the state to bar sprayings after April 15 next year of agricultural herbicides containing the chemical dicamba, which has been linked to crop damage across the U.S. farm belt, a state spokeswoman said on Friday.

The recommendation aims to protect plants vulnerable to the chemical and, if adopted, would prevent most Arkansas farmers from spraying dicamba weed killers on growing soybeans, a key selling point for products manufactured by Monsanto Co, BASF and DuPont.

Dicamba has long been used in the United States to kill weeds before fields were planted. Its use spiked, though, after regulators last year approved a new formulation that allowed farmers to apply it to soybeans that have emerged from the ground and are engineered by Monsanto to resist the chemical.

Last month, Arkansas temporarily banned the use and sale of dicamba after farmers complained the herbicide was drifting away from where it was sprayed and damaging crops.

The U.S. Environmental Protection Agency (EPA) is reviewing label instructions for dicamba weed killers following reports of crop damage in states from Arkansas to North Dakota.

“I think Arkansas has decided what the solution to this problem is,” Andrew Thostenson, a pesticide specialist for North Dakota State University, said about the spraying deadline.

“I think everybody in the United States, including the EPA, is going to be looking at what Arkansas did.”

Arkansas previously blocked Monsanto’s dicamba herbicide, XtendiMax with VaporGrip, because the company did not provide testing data that state officials wanted. The state approved BASF’s herbicide.

Thirty-three other states approved both products.

Monsanto said the task force’s recommendation will put Arkansas farmers at a disadvantage to those in other states. The company is in talks with the EPA, which “is interested in achieving national uniformity with dicamba regulation in order to avoid a state patchwork,” Monsanto spokeswoman Charla Lord said.

BASF had no immediate comment. DuPont did not immediately respond to a request for comment.

The task force also advised Arkansas to request more independent and university testing on new seeds and chemicals before they come to market, said Adriane Barnes, spokeswoman for the Arkansas Agriculture Department.

The recommendation will be reviewed by the governor and state agencies before a decision is made. No timeline has been disclosed.

They said products intended to be used together, such as Monsanto’s dicamba-resistant Xtend soybeans and XtendiMax herbcide, should be ready to use at the same time.

Monsanto sold Xtend soybeans to growers in 2016, a year before they were able to apply XtendiMax over growing crops. That led some farmers to spray dicamba illegally, causing damage to plants, according to weed specialists.