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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.

WSU Wheat Beat Podcast Episodes


Narrow Windrow for harvest weed seed control.
Herbicide resistance is of growing concern to wheat growers in the Pacific Northwest. Harvest weed seed control (HWSC) is an innovative, non-chemical approach developed in Australia that takes advantage of seed retention at maturity in many dominant annual weed species. Harvest weed seed control systems are focused on the management of chaff material in which most weed seed resides. Although HWSC has not been fully evaluated in the PNW, early work suggests that it can be an effective tool in an integrated weed management program. The choice of which particular HWSC system to use is dependent on the constraints of the cropping systems in which they are used and the specific needs of the grower. This publication discusses the various HWSC systems and their potential suitability for PNW wheat production systems across rainfall regions.

Tools

Herbicide Resistance Weeds Map

Functionality: The Herbicide Resistance Weeds Map allows you to see what herbicide-resistant biotypes have been identified in counties in eastern Washington and adjoining counties in Idaho and Oregon. New

Herbicide Resistance Weeds Map

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: Wheat

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.

Herbicide Mechanisms of Action: Pulse Crops

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

Wheat Academy logo with WSU cougar.

Ian Burke’s presentations:

Washington State University