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Manage Resistant Weeds with these Key Strategies

January 17, 2018
This agronomic image shows the weed marestail.

Marestail seeds

As herbicide resistance becomes a greater issue in many key corn- and soybean-growing regions, it’s important to be thinking about the things you can do to face the problem head-on. University and industry research has cast doubt on common assumptions about managing resistant weeds and is rewriting some of the “rules” as a result.

Use multiple, effective modes of action:

Weed scientists conducted a study and found that consistent use of multiple, effective herbicide modes of action (MOAs) were effective in delaying the development of resistance. A field that received an average of 2.5 MOAs per application from 2004 to 2006 was 83 times less likely to produce glyphosate-resistant waterhemp seeds than a field that received 1.5 different MOAs per application.

Don’t rely on herbicide rotation alone:

Weed seeds carrying resistance can lie dormant, then germinate after 2 years and face the same herbicide that failed to control their parent weeds. If you’re using just one MOA in those years, it’s more likely that a resistant population will develop.

A strong herbicide program should include pre-emergence and post-emergence herbicides, both with multiple effective MOAs. For control of resistant weeds in soybeans, we recommend starting with Boundary® 6.5 EC herbicide (Groups 5 and 15), BroadAxe® XC herbicide (Groups 14 and 15) or Prefix® herbicide (Groups 14 and 15), followed by Flexstar® GT 3.5 herbicide (Groups 9 and 14), each containing 2 MOA’s. When combined, a full pre- and post-emergence program using these products will contain 3 to 4 different effective modes of action.

For control of resistant weeds in corn, we suggest using Acuron® or Acuron Flexi corn herbicide. Acuron combines 4 active ingredients and has 3 effective MOAs (Groups 5, 15 and 27) while Acuron Flexi combines 3 active ingredients and has 2 effective MOAs (Groups 15 and 27). Both herbicides offer application flexibility, from 28 days pre-plant up to 12” corn for Acuron and 28 days pre-plant up to 30” corn for Acuron Flexi, and work well in 1 or 2-pass systems. A 2-pass system can also include a post-emergence application of Halex® GT corn herbicide (Groups 9, 15 and 27) for an additional mode of action.

For more tips on how to win the battle against resistant weeds, visit ResistanceFighter.com.

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