The Environmental Protection Agency has given Mississippi catfish growers the green light to use diuron in their battle against a blue-green algae that, when present in catfish ponds, is linked to off-flavor fish.

An algaecide, diuron was approved by the EPA March 21 under a Section 18 emergency exemption label. Growers were able to use the product in 2001, too, under a previous Section 18 label.

“Diuron is a critical tool catfish growers use to produce high-quality, farm-raised catfish,” says Hugh Warren, executive vice president of the Catfish Farmers of America, headquartered in Indianola, Miss.

Off-flavor catfish has been a problem for growers for several years. Warren says, “Many farmers believe this algaecide is extremely effective in reducing or eliminating the blue-green algae in ponds that is often attributed to the off-flavor problem.”

The Section 18 label for diuron remains in effect from April 1 to Nov. 30, 2002, and applies to Diuron 80 W, manufactured by Drexel Chemical Co., and Nautilus Aquatic Herbicide, manufactured by Griffin LLC.

According to the EPA, the diuron products may be applied on commercial levee-contained catfish ponds by pouring a pre-mixed slurry from a bucket directly into the pond on the outflow side of the operating aerator. The approved application rate is 0.5 ounce of product, or 0.4 ounce active ingredient, per acre-foot, every seven days, not to exceed nine applications per year.

A maximum of 70,000 acres of catfish ponds in Mississippi may be treated under the Section 18 exemption.

The EPA label mandates that mixers, loaders and applicators of diuron wear a long-sleeved shirt, long pants, chemical resistant gloves, shoes and socks.

This is the fifth year Mississippi catfish growers have requested an emergency exemption for diuron, according to Peter Caulkins, active director of EPA's registration division for the Office of Pesticide Programs.

EPA evaluated progress towards registration as one of the factors in reaching decisions on emergency exemption requests. EPA has received a registration petition for this use, but it is not on the 2002 work plan. Nonetheless, progress toward registration is sufficient for the purposes of this year's request.