The US Environmental Protection Agency (EPA) has said it will only partially implement last week’s order by the US 9th Circuit Court of Appeals to vacate its registration of the controversial herbicide active ingredient dicamba and halt sales. It cited potential difficulty for clearing weeds to protect crops already planted.

The San Francisco federal court also ordered Bayer, Corteva and BASF to stop selling or distributing dicamba products, while blaming the EPA for its continued use.

Encouraged by US agriculture secretary Sonny Perdue, who called dicamba a “valuable tool for US farmers,“ the agency said it would agree to halt the sale and distribution of the chemicals, but would allow farmers to spray fields with “existing stocks that were in their possession on Jun. 3, 2020, the effective date of the court decision.”

The herbicide launched by Monsanto in 1962 has been eyed critically by farmers and environmental activists because of its tendency to drift and damage crops in neighboring fields. The problematic has led to many lawsuits. Most recently, in February this year, a jury found Bayer and BASF liable for drifts that the state of Missouri’s largest peach grower said caused of $265 million to his crops.

Due to the drift disputes, usage figures showed the herbicide’s popularity waning until Monsanto , which was bought by Bayer in 2018. introduced its RoundupReady Xtend seeds for soybean crops engineered to withstand both dicamba and glyphosate. The EPA also approved similar formulations by other agrochemical producers, which led to increased spraying and thus more drift, as the court noted.

In a scathing criticism of the EPA, the California judges said the agency “substantially understated” the acreage planted with dicamba-tolerant crops in 2018, refused to acknowledge the extent of crop damage and, overall, failed to recognize the anticompetitive economic effects the registrations would have in the soybean and cotton industries. Some farmers felt compelled to buy Bayer’s seeds to avoid damage from dicamba, it said.

The US agriculture trade journal DTN estimated that 60 million acres of dicamba-tolerant cotton and soybeans were slated for 2020 planting, a land mass equal to more than half the size of California.

Reacting to the court’s initial ruling last week, Bayer’s US arm said the company “strongly disagreed” with it and would await direction from the EPA on actions it might take in response. BASF also took issue with the decision, which it said “could be devastating to tens of thousands of farmers.” The Ludwigshafen-based group also vowed to use “all legal remedies available to challenge this order.“

The Center for Food Safety, which launched the initial legal action, said the EPA was ignoring the “well-documented and overwhelming evidence of substantial drift harm to farmers.” Legal director, George Kimbrell, said the organization will challenge the EPA’s failure to abide “as expeditiously as possible.”

Dicamba also is being studied as a potential carcinogen. In a paper published on May 1, a group of National Institute of Environmental Health Sciences and National Cancer Institute scientists conducting an ongoing research project on agrochemicals, said that exposure to dicamba in agricultural settings can lead to an “elevated risk” of liver cancer