Weed Warriors: Location, Location

March 8, 2013 08:32 PM
Weed Warriors: Location, Location

Multiple herbicide sites of action improve weed control

Farmers who wrestle with tough-to-control weeds know all too well the importance of rotating herbicide chemistries, or using multiple modes of action. To take weed control to the next level, tune into the concept of herbicide site of action, advises Bob Hartzler, Iowa State University Extension weed scientist.

While the industry often uses the two terms interchangeably, there is a distinct—and important—difference between them, he says.

Mode of action is how a herbicide controls a weed. Site of action is where the herbicide controls the weed. The sites of action that herbicides tackle are located in a variety of areas on a plant—for instance, below ground in weed roots or above ground in foliar parts of plants.

Farmers who use multiple sites of action in their herbicide program often find that obtaining a good control outcome is easier to achieve and more comprehensive in the process. That’s good news for farmers who have seen their weed problems, especially resistance, multiply in recent years. A 2012 farmer survey conducted by BASF reports that roughly 50% of U.S. farmers are experiencing some level of weed resistance in their fields today.

As new technologies come into the marketplace, farmers can benefit from determining their sites of action, says Jim Bloomberg, Bayer CropScience crop development manager for corn and soybeans.

"When you use a new product, make sure it doesn’t work on the driver weed you’re trying to control at the same site of action as the product you’re already using," he recommends.

The Weed Science Society of America groups control products with similar sites of action together by group numbers from 1 to 29. This number, often included on the product label, is an easy way for farmers to identify products and premixes.

You can e-mail Rhonda Brooks at rbrooks@farmjournal.com.

For more information on herbicide sites of action, visit www.FarmJournal.com/weed_warriors

FJ Herbicide Chart p48

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