You are here

6 points to remember about atrazine

Atrazine is in a perennial battle between the agricultural chemical industry and environmental groups. Caught in the middle are state and federal regulators and the farmers who actually apply atrazine on corn, sorghum, and other crops.

The latest spat is over a 2009 reevaluation of triazine herbicides (to which atrazine belongs) by the Obama administration. This follows a regularly scheduled triazine federal reregistration that the EPA approved under the Bush administration.

What does this mean to you? It's possible that atrazine could be banned under this reevaluation. That's what happened in the European Union in 2003, when regulators banned atrazine due to concerns about its impact on health and the environment.

It's also possible that more restrictions could result, such as lower rates Or, you could continue using this popular corn herbicide as you always have.

Here are some points to keep in mind about atrazine and its future use.

1. If you grow corn, you likely use atrazine.

It's used on over 60% of U.S. corn acres, says Chuck Foresman, global corn R & D lead or Syngenta, an atrazine manufacturer.

“There are more than 60 premix products that have atrazine in them,” he says. “Over the past 15 years, there is not a single product in corn that doesn't recommend the use of atrazine for a partner mix.

“Nothing will take its place,” he adds. “As an example, nothing is as effective on morningglory as atrazine. It also improves herbicide performance with critical weeds like giant ragweed and waterhemp. Atrazine is a relatively inexpensive but an efficacious product.”

“Waterhemp is a tough weed to control, and atrazine is a big help in the farmer's ability to control that weed,” says Darrin Ihnen, a Hurley, South Dakota, producer.

Leon Corzine, an Assumption, Illinois, farmer, compares atrazine to a crescent wrench in his toolbox.

“I might not use it all the time, but I might have a need for it – just like a crescent wrench for fixing machinery,” he says.

2. Current rates are lower than past ones.

Thirty years ago, much concern existed regarding soybeans planted behind corn to which atrazine had been applied. That's because multiple-pound-per-acre atrazine rates would carry over and damage the next year's soybeans.

No more. Use rates are much lower than what they used to be. “We never apply more than 1 pound per acre, and in some cases, it's only three quarters of a pound,” says Ihnen. “We use a half rate with our preemergence herbicide and come back with a half rate with our postemergence herbicide. That's more than enough to give the residual control to help control small-seeded broadleaves and help control grasses.”

3. Atrazine is safe to use so far.

That's because the previous reregistration processes and the current reevaluation show it is.

In the 2006 reregistration, EPA ruled in atrazine's favor after considering 6,000 studies and 80,000 public comments. The 2009 reevaluation was partially in response to a 2009 New York Times article citing that atrazine may be more dangerous at lower concentrations than previously thought. Standards could change if EPA rules atrazine is more hazardous to health than previously thought.

Currently, EPA standards allow 3 parts per billion (ppb) or less of atrazine to be present in drinking water. That's already a stringent standard, say Syngenta officials. The World Health Organization has set a 100 ppb threshold for drinking water.

Atrazine gained a boost in 2011 when a multiyear federal Agricultural Health Study found no consistent association between atrazine and cancer rates on farmers, farm spouses, and pesticide applicators. The study, which started in 1993, focused on more than 20 pesticides, including atrazine. The only possible concern was thyroid cancer among users. However, no firm relationship was established between atrazine exposure and thyroid cancer.

4. Atrazine saves your soil.

Trizane herbicides like atrazine help slice the need for tillage and the conversion of land to crop production. This reduces soil erosion from U.S. cropland by 56 to 85 million tons per year, according to an analysis by Paul Mitchell, a University of Wisconsin agricultural economist. Based on these reductions, triazine herbicides provide $210 to $350 million annually in benefits from reduced soil erosion.

“If atrazine is no longer available, people will have to revert to tillage to control tough weeds,” says Foresman.

5. Atrazine fits with resistance management.

Atrazine adds another mode of action to your herbicide mix.

“It helps with weed resistance (to herbicides) and all the problems associated with it,” says Ihnen.

“Many weeds showing resistance to glyphosate are sensitive to atrazine,” says Mike Owen, Iowa State University Extension weeds specialist. “That suggests it will be an important component of weed-control programs.

However, it's not foolproof. There are biotypes of waterhemp that resist triazines. In the 1990s, for example, resistance in Illinois popped up to triazines and ALS inhibitors.

In 2009, scientists discovered a waterhemp biotype with four-way resistance to triazines, gyphosate, PPOs, and ALS inhibitors, says Aaron Hager, University of Illinois Extension weed specialist.

6. Will atrazine be banned?

“Atrazine won't be banned if objective science prevails,” says Owen.

New rules like lower use rates may be more likely. That wouldn't bode well for corn farmers, says Foresman. Rates are set as low as they can be.

“If we make further adjustments in cutting rates, I fear we will get into a situation where the compound will no longer be as consistent, and we will sacrifice weed control,” he says.

Read more about