Herbicide Resistance Resources

Herbicide-resistant weeds are becoming increasingly common in the Pacific Northwest, threatening the economics and sustainability of farming systems. Herbicide-resistant weed biotypes are selected for and will increase in the population through repeated use of the same or similar herbicides. Italian ryegrass, downy brome, wild oats, Russian thistle, mayweed chamomile, and prickly lettuce are just a few of the many weed species with biotypes resistant to commonly used herbicides. The resources on this page will help you understand how herbicide resistance occurs, how to manage weeds to slow the rate of herbicide resistance development, and what to do if you suspect you have a resistant biotype on your farm.
This article was published in the Capital Press by Matthew Weaver on April 25, 2019. The Capital Press provides limited free access to the contents of its website for non-subscribers.
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Featured Herbicide-Resistant Weed

Mayweed Chamomile

Mayweed chamomile population segregating for resistance to an ALS inhibitor (Group 2) applied to spring barley in 2013. Ten years ago, mayweed chamomile was easily controlled with ALS inhibitors, but today, most mayweed chamomile populations in the PNW can no longer be controlled with ALS-inhibitor herbicides.

Related Publications

Weed Control Reports Excerpts

2018 Weed Control Reports

2017 Weed Control Reports


Tools

Herbicide Mechanisms of Action: Wheat
Functionality: 
Allows growers to query a database of herbicide trade names, active ingredients, mechanisms of action, and Washington weed species with confirmed resistance to one or more herbicides. Growers can search by trade name to find out what active ingredient(s) are in a herbicide product, what mechanism(s) of action the active ingredient(s) represent, what chemical family each active ingredient is in, and whether there are any weed biotypes in Washington with confirmed resistance to that mechanism of action.

 Herbicide Mechanisms of Action: Pulse Crops
Functionality:
 Like the tool for wheat, the pulse crops tool allows growers to query a database of herbicide trade names, active ingredients, mechanisms of action, and Washington weed species with confirmed resistance to one or more herbicides. Growers can search by trade name to find out what active ingredient(s) are in an herbicide product, what mechanism(s) of action the active ingredient(s) represent, what chemical family each active ingredient is in, and whether there are any weed biotypes in Washington with confirmed resistance to that mechanism of action. The tool also allows growers to search the database by active ingredient, mechanism of action group, or resistant weed.

Additional Resources

Youtube Video

Integrated weed management (IWM) strategies are critical for effective long-term management of weeds in the agroecosystem. This video summarizes the biological framework for integrated weed management and summarizes an approach to developing a weed management plan.

Wheat Academy Presentations

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Ian Burke’s presentations:

Washington State University