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BMPs are vital with re-registration of herbicide atrazine

As part of the re-registration of the popular herbicide atrazine, farmers should adopt best management practices, or BMPs, to prevent runoff and ensure that atrazine remains a viable product, says a University of Missouri Extension water quality specialist.

Pesticide re-registration involves reviewing the scientific data for pesticides registered before November 1984 to ensure they meet today’s scientific standards, explains Bob Broz. “Re-registration does not imply that there is anything wrong with the product, but simply that it makes sense to ensure that products meet the most current standards.”

Atrazine has been in use for 50 years, and continues to be one of the most effective products for control of grasses and broadleaf weeds in corn, grain sorghums and sugarcane fields. Based on the review of available scientific studies, the U.S. EPA determined in 2000 that atrazine is not likely to cause cancer in humans. Additional studies in 2003 and 2006 verified that atrazine is not carcinogenic to humans, Broz notes.

Key Points

Atrazine re-registration means more runoff scrutiny in the Corn Belt.

A study finds that two Missouri watersheds exceed safe atrazine levels.

Farmers can implement best management practices as prevention.

Starting in 2009, EPA has been looking at the characteristics of atrazine and how they affect certain ecological indicators. Levels considered safe for humans may not be deemed acceptable for other more sensitive species.

Without sound management practices, excessive runoff can create problems. Forty representative watersheds were selected in the Midwest for a study to determine the levels of atrazine in streams. Three of these watersheds, one in Nebraska and two in Missouri, exceeded trigger levels for atrazine. Under the latest re-registration agreement, EPA has more authority to limit or ban atrazine if runoff levels are over set target values.

“Even though the watersheds where testing was done are fairly small, about 20,000 acres each, these represent similar soil conditions in more than a million acres,” Broz says.

“Atrazine has provided the ability to control grasses and weeds in no-till farming systems. Without such weed control, many farmers may never have adopted the concept of conservation tillage. Atrazine has become an important tool in promoting no-till and minimum-tillage farming systems that save soil and reduce water runoff,” he adds.

Broz believes that if farmers can determine and implement the BMPs that work effectively at preventing atrazine runoff, they should be able to continue using atrazine as a viable product.

Farmers use atrazine to control weeds on more than half of the corn, 65% of the grain sorghum and about 90% of the sugarcane grown in the U.S.

To read more about weed and pest management, visit

Thomas is an information specialist for MU Cooperative Media Group

This article published in the January, 2011 edition of MISSOURI RURALIST.

All rights reserved. Copyright Farm Progress Cos. 2011.