CHICAGO (Reuters) – Arkansas agricultural regulators stuck with a proposal on Wednesday to prohibit sprayings of a controversial weed killer after mid-April, despite a lawsuit over the plan by manufacturer Monsanto Co.

The state’s plant board decided to move forward with a ban on the use of dicamba-based herbicides from April 16 to Oct. 31, after state lawmakers recommended last month that the panel review its recommendation.

The ban threatens to hurt demand for the products made by Monsanto and rival BASF SE because the chemicals are designed to be sprayed on dicamba-resistant crops during the summer growing season.

The United States faced an agricultural crisis last year caused by new versions of the herbicides, which farmers and weed experts said evaporated and drifted away from where they were applied, damaging millions of acres of crops that could not tolerate dicamba.