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Why is it important to tank-mix
      multiple effective modes of action?

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Mode of Action

The term mode of action (MoA*) is defined as how a particular herbicide acts on a plant.  

Why is it important to use multiple effective sites of action in each herbicide application?

For years, the recommendation was to annually rotate herbicide chemistries. But recent research has shown that simply rotating chemistries doesn't prevent resistance. Using multiple effective sites of action in each herbicide application is the key.

The University of Illinois compared the difference between rotating herbicide chemistries versus multiple effective sites of action in a single application. They discovered that when treated with at least two effective sites of action per application, weeds were 83 times less likely to develop resistance, compared to rotating herbicide chemistries.

The Weed Science Society of America has a herbicide classification numbering system to identify sites of action. Several active ingredients may have the same site of action so they share a site of action group number. Becoming familiar with these numbers is a way to ensure multiple sites of action get used.

Also, it’s important to understand which sites of action are effective on a specific weed species. Using a site of action where resistance has already developed is no better than using a single site of action that causes resistance.
Use the Take Action Herbicide Look Up Tool to find the site of action group numbers in commercial herbicide brands and then begin planning premix or tank-mix partners.

*Active ingredients having the same MoA can be grouped and classified together.