The US Environmental Protection Agency (EPA) has canceled the registration of the herbicide flubendiamide, believed to pose a risk to fish, as the two manufacturers, Bayer CropScience of Germany and Nichino America, a subsidiary of Japanese chemical producer Nihon Nohyaku Co. have refused to stop making it.

EPA said it had issued a time-limited registration to the companies “with conditions that were understood and agreed upon.” These were that, if unreasonable adverse effects on the environment were found, the companies would submit a request for voluntary cancellation of all flubendiamide registrations within one week of notification by the agency.

After being informed of the finding on Jan. 29, Bayer and Nichino were asked to submit a request for voluntary cancellation by Feb. 5, 2016, but declined to do so, EPA said. Bayer, which maintains that the product is safe, has asked for a review of the decision.

US law requires a final ruling by the administrative law judge within 75 days of receiving the hearing request. In the interim, EPA said crops properly treated with flubendiamide or that may be treated with existing stocks can still be sold legally. Provisions on how to handle existing stocks are to be finalized after the products have been canceled.

Flubendiamide is registered for use on more than 200 crops in the US, including soybeans, almonds, tobacco, peanuts, cotton, lettuce, alfalfa, tomatoes, watermelon, and bell peppers, with some crops having as many as six applications per year.

Bayer’s insecticide Belt is applied to some 2-2.5 million acres of crops in the US, the German group’s US representative said, with use concentrated in California and Arizona, the South and Southeast.

EPA said required studies showed flubendiamide breaks down into a more highly toxic material harmful to species that are an important part of aquatic food chains, especially for fish, and is persistent in the environment. Therefore, continued use of the product would result in unreasonable adverse effects on the environment.