MADISON – As the 2011 growing season nears, Wisconsin corn growers are reminded to follow the state’s rules on the use of the corn herbicide atrazine, remind state agriculture officials.

“Atrazine or products that contain atrazine cannot be used within an area where its use is prohibited,” said Stan Senger, environmental quality section chief, Department of Agriculture, Trade and Consumer Protection. “There are 101 atrazine prohibition areas in Wisconsin that cover approximately 1.2 million acres of land. This includes land along the Lower Wisconsin Riverway.”

Prohibition areas are established when atrazine levels in a private well exceed the state health standard of three parts per billion.

Farmers and pesticide applicators need to check the label and identify the active ingredients in the herbicide and not rely on the product name.

“Remember that many ‘premix’ herbicide products contain atrazine even though you would not know this from the product name itself,” Senger said. “Any herbicide product that lists atrazine as an active ingredient cannot be used in a prohibition area.”

Some of the most common atrazine-containing premix products used in Wisconsin include: Lumax®, Keystone®, Bicep II Magnum®, Harness® Xtra and Marksman®. Products that contain atrazine as a single active ingredient include Aatrex® 4L and Aatrex Nine-O®. Senger pointed out that more than 80 products are registered for use in Wisconsin that contain atrazine so he encourages applicators to carefully read product labels.  

Knowing the location of atrazine prohibition areas is also critical.

Maps of Wisconsin’s atrazine prohibition areas along with other product restrictions can be found on the department’s website.

Senger advises growers to review the maps each year for possible changes. “Most of the prohibition areas were created 10 or more years ago but through well sampling, laboratory tests and environmental investigations, we may add or modify an area through a rule revision,” Senger said.

Sauk County has a new prohibition area that is adjacent to the Lower Wisconsin River Valley. In Columbia County, additional restricted acreage near Pardeeville connects two neighboring prohibition areas. These areas will take effect on May 1, 2011.

Finally, the mixing and loading of any atrazine product is prohibited unless the mixing and loading is done over a spill containment pad. Requirements for spill containment pads can be found here.

For fields that are not located in a prohibition area, Wisconsin has additional restrictions on the use of atrazine that apply statewide. On coarse texture or sandy soils, atrazine can be applied at a maximum rate of 0.75 pounds per acre per year. On medium texture or loam soils, atrazine can be applied at 1.0 pound per acre if the field received atrazine the previous year or 1.5 pounds per acre if it did not. Farmers can apply atrazine from April 1 through July 31. No fall applications are allowed.

For more information about atrazine regulations in Wisconsin, contact Jeff Postle, (608) 224-4503 or Rick Graham, (608) 224-4502.