How to Balance ALS Herbicides Effectively

ALS herbicides have taken some punches over the years, but they can still pack a potent wallop of their own. The secret is learning how to best balance them with other chemistries to tap into their effectiveness. 

The bad news? Dozens of ALS-resistant incidents have popped up across the world. The good news? This herbicide class (Group 2) can still provide effective control over a broad spectrum of broadleaf weeds and grasses. 

“Although we have resistance to several chemistries today, including ALS, glyphosate, PPO, triazines, growth regulators, HPPD and ACCase, we still get a lot of use from these products,” says Curtis Thompson, Kansas State University weed scientist. 

The key, Thompson says, is to develop a weed-control strategy that combines pre-emergence residual herbicides with postemergence herbicides (when needed). 

“Avoid the repeated use of a single chemistry that allows for selection of resistant biotypes,” he advises. 

Thompson says application timing discussions are hot right now among researchers, retailers and farmers alike. He advises farmers to check with their local university Extension for the latest recommendations.  

Additionally, consider the following four-point checklist to protect the effectiveness of ALS herbicides: 

  1. Know how the chemistry fits with target weeds in a particular field. Be aware of resistance issues ALS has with weeds such as marestail, waterhemp, Palmer amaranth, cocklebur, giant foxtail and others.
  2. Integrate ALS herbicides with other chemistry groups that havedifferent modes and sites of action. 
  3. Fold in cultural practices such as crop rotation, tillage and cover crops to help manage weeds.
  4. Stop weeds before they deposit seeds into the soil seedbank, where they can cause problems for years to come.

Experts agree: In the era of tough-to-control and resistant weeds, an economic threshold approach no longer makes sense. Instead, strive for an integrated, zero-tolerance approach to weed control. 

Photo Credit: ©2012 AgStock Images / David Halsey

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