The U.S. Environmental Protection Agency has given pesticides manufacturers a deadline to agree to new restrictions on applying three farm pesticides that pose a threat to Pacific salmon, or the agency will take action itself.

GRANTS PASS — The U.S. Environmental Protection Agency has given pesticides manufacturers a deadline to agree to new restrictions on applying three farm pesticides that pose a threat to Pacific salmon, or the agency will take action itself.

A letter from the EPA gives manufacturers of diazinon, malathion and chlorpyrifos until May 13 to say whether they will comply with the restrictions.

The chemicals have been found by federal biologists to interfere with salmon's sense of smell, making it harder for them to find food, avoid predators and return to native waters to spawn.

There was no immediate word from manufacturers Makhteshim Agan of North America, Inc., Cheminova, Inc., or Dow AgroSciences LLC on what they planned to do.

"We have obviously received the latter," said Dow AgroSciences spokesman Garry Hamlin. "We are carefully evaluating it. We will respond to EPA at a later date."

Scott Rawlins, director of government relations for Makhteshim Agan, said they were meeting with EPA over the issue on Wednesday.

The EPA action comes 18 months after NOAA Fisheries Service found that the pesticides threaten the survival of 27 species of salmon and steelhead in the West. Anti-pesticide groups had initially sued EPA over the issue in 2001.

"For nearly a decade now, we have been urging and prompting the government to take appropriate steps to protect salmon and steelhead," said Aimee Code of the Northwest Coalition Against Pesticides. "Pretty much every step in this confrontation we had to file a lawsuit. Now we are seeing EPA taking a step to finally get the long-term protections prescribed by (NOAA Fisheries) on the ground."

NOAA Fisheries has suggested varying buffer strips and application strengths to keep the pesticides out of salmon streams, including those that do not run all the time.

The letter from Richard P. Keigwin, Jr., DPA director of the Pesticide Re-evaluation Division notes that the agency has been going back and forth with pesticide makers over the detailed restrictions since Dec. 7, 2009.

"If the registrants are not prepared to adopt all of these limitations, EPA will pursue administrative procedures under the Federal Insecticide, Fungicide, and Rodenticide Act to compel implementation of all limitations," he wrote.