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Weed Resistance Management

  • 2 herbicides can share the same mode of action, but still have a different site of action, making site of action the most important consideration for resistance management.
  • Full rates of herbicides at the proper timing need to be applied to help avoid weed escapes, increase residual soil herbicide activity and keep resistance at a minimum.

The list of weeds with documented resistance to herbicide modes of action and cross resistance grows each year. Managing weed resistance successfully combines cultural and rotational actions taken by farmers along with herbicide programs that include multiple effective sites of action (SOA) at labeled use rates and timing. Key facts:

  • Mode of Action (MOA) refers to the plant processes affected by the herbicide. Example: Cell membrane disruptor
  • Sites of Action (SOA) can be defined as the biochemical site inside a plant that the herbicide blocks or inhibits. Example: PPO inhibitor
  • 2 herbicides can share the same MOA, but still have different SOA. MOA is “how” and SOA is “where” (the specific protein the herbicide binds to and inhibits function), making SOA the most important to consider for resistance management.
  • Premixes offering multiple active ingredients may or may not offer multiple SOA. A nice reference that lists premixed herbicides by their trade name can be found here.

Why Should You Use Effective Weed Resistance Management Strategies?

  • Make a profit or increase profit potential
  • Investment in land value
  • Control weeds that are no longer controlled with post-emergence applications
  • Resistance management