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The 2016 WSU Weed Control Report Has Arrived!

Photo courtesy of graduate student John Spring.

Photo courtesy of graduate student John Spring.

The 2016 WSU Weed Control Report is now available on the Wheat and Small Grains website. The annual report summarizes the results from field studies conducted by Ian Burke, Drew Lyon, and their staff. Financial support for the studies was provided by the Washington Grain Commission, the USA Dry Pea & Lentil Council, the Mel & Donna Camp Endowment, and by several agrichemical companies. The research was conducted in winter wheat, spring wheat, chemical fallow, grasslands, alfalfa, chickpeas, and dry pea.

Weeds investigated in 2016 included rattail fescue, mayweed chamomile (a.k.a. dog fennel), catchweed bedstraw, rush skeletonweed, Russian-thistle, common lambsquarters, wild oat, Italian ryegrass, downy brome, smooth scouringrush, and volunteer buckwheat. Two studies looked at Talinor, a new herbicide from Syngenta, in winter wheat. Several studies were conducted in chickpea to look at pyridate, previously sold as Tough herbicide, and paraquat applied at the cracking stage. Neither option is currently labeled for use in chickpea, but you can see what the potential for these treatments are. Data from these studies may be used to help support possible labeling in the future.

In addition to the 2016 report, annual reports dating back to 2013 are on the Wheat and Small Grains website.

For questions or comments, contact Dr. Drew Lyon at or 509-335-2961.

Jointed Goatgrass Biotype Resistant to Beyond Discovered in Eastern Washington

The first case of jointed goatgrass resistant to imazamox, the active ingredient in Beyond herbicide, has been confirmed in Eastern Washington. A team of Washington State University scientists, led by Dr. Ian Burke, publicly announced their findings in the January 2017 issue of Wheat Life magazine.

Clearfield wheat varieties were first planted in Eastern Washington on a widespread basis beginning in the fall of 2003. The fact that it has taken 13 years to discover the first imazamox-resistant jointed goatgrass biotype is a bit of a surprise. Ian Burke said “If you had asked me back when I started working on this in 2006 when to expect to see resistance to Beyond in jointed goatgrass, I would have said ‘we should see it already!’”

The resistant biotype is 144 times more resistant than susceptible goatgrass plants. To see even a little response in the resistant plants, researchers had to use 6x the labeled use rate of Beyond. Jeannette Rodriguez, a WSU graduate student, is working to identify the mechanism of resistance. It is known that resistance in this instance was not the result of a cross between Clearfield wheat and jointed goatgrass.

Growers and fieldmen should scout jointed goatgrass patches in fields that they manage and submit samples that they have concerns about to the WSU Herbicide Resistance Testing Program. The Extension publication “Strategies to Minimize the Risk of Herbicide-resistant Jointed Goatgrass” provides information on the control of jointed goatgrass with an emphasis on prevention and management of herbicide resistance.

BASF issued the following statement in response to this discovery: “BASF is supporting WSU research aimed at preserving the long-term benefits of the Clearfield® Production System – with an emphasis on resistant jointed goatgrass. A multifaceted resistance management program is essential to preserve the long-term benefits of Beyond herbicide and the Clearfield Production System. Wheat producers are asked to help protect and prolong the usefulness of these technologies by following the specific recommendations and requirements highlighted in the Clearfield Stewardship Guidelines to help prevent the onset of herbicide resistance in weeds.”

For more information, contact Dr. Ian Burke at or 509-335-2858.

Web-Enabled AMS Sprayer Mix Calculator Now Available

Earlier this year we introduced a handy calculator that uses data from a 1264_rogator_spraying_cornstandard water quality test to determine the amount of AMS to add to your spray tank, in pounds of AMS per 100 gallons of water. The calculator was created as a pdf file and it did not work well on many mobile devices so we put together the AMS Sprayer Mix Calculator which is web-enabled and works on computers and mobile devices.

Like the previous calculator, the new calculator uses the equation developed at North Dakota State University (Nalewaja and Matysiak, 1993) to determine the required amount of AMS needed to neutralize the effects of cations in the water on glyphosate activity. Adding more AMS than called for to neutralize the effects of cations may improve glyphosate activity by providing extra N that helps weak acid herbicides like glyphosate pass through cell membranes. The addition of 8.5 to 17 pounds of AMS per 100 gallons of water is generally recommended to improve glyphosate activity. Liquid forms of AMS are equally effective if used at equivalent rates.

Give the new AMS Sprayer Mix Calculator a try and see what you think. Questions may be directed to Drew Lyon at (509-335-2961).

Winter Wheat Herbicide Efficacy Tables Helps Growers Narrow Herbicide Options

talinor-study-2016-tarweedWeeds are the bane of many farm operations, and consequently, farmers spend more money on herbicides than any other production input other than fertilizer. However, it can be difficult to choose what herbicide or herbicides to use. There are many herbicides to choose from, each with their own strengths and weaknesses. Additionally, there are a myriad of weed species competing with wheat for water, light, and soil nutrients. Although the Winter Wheat Herbicide Efficacy Tables will not tell wheat growers what herbicide or herbicides to use, it will help growers narrow their herbicide options based on the weeds that they are most concerned with.

In addition to the Winter Wheat Herbicide Efficacy Tables, The Herbicide Mechanism of Action (MOA) tool was recently released. Both of these tools were designed to harness the research generated at WSU and elsewhere to help growers make more informed decisions for their farm operations. Development of these tools was partially supported by funds from the Washington Grain Commission. Feedback on either of these tools is welcome!

Contact Drew Lyon ( or 509-335-2961) with your questions or suggestions for improvement.

Recent Rains Will Bring on Winter Annual Grass Weeds


Figure 1

Recent rains are likely to result in the germination and emergence of winter annual grass weeds such as downy brome, jointed goatgrass, and feral rye in winter wheat fields throughout Eastern Washington. Many winter wheat growers wait until the spring to apply herbicides to control these weeds. The argument for this approach is that they want to have all their weeds emerged so they can kill them all. They know that they get additional weed emergence over the winter. Despite this argument, fall is the best time to control winter annual grass weeds in winter wheat.

Research has shown that downy brome that emerges within seven to ten days of wheat emergence causes significant yield loss in winter wheat. Downy brome that emerges more than three weeks after winter wheat is much less competitive than earlier emerging downy brome. Growers who delay spraying until spring risk allowing fall-emerged downy brome to compete all winter with wheat. Worse, spring-applied herbicides are often inconsistent in controlling downy brome.

In a summary of 15 years of field data in Eastern Washington, Nevin Lawrence, former Ph.D. weed science student studying under Dr. Ian Burke, found that Outrider, Olympus, and PowerFlex all provided superior downy brome control when applied in the fall rather than the spring (see figure). Downy brome control did not differ for Beyond applied fall or spring. Beyond may only be applied to Clearfield wheat varieties.

What has been reported for downy brome (see figure 1) is likely also true for the other winter annual grass weeds. So whether your problem is with downy brome, jointed goatgrass, or feral rye, the fall is almost always the best time to implement control measures, especially when early fall rains bring these weeds up in September or October.

For more information on controlling downy brome in winter wheat, including herbicide recommendations, see Integrated Management of Downy Brome in Winter Wheat, a Pacific Northwest Extension Publication – PNW668. Similar information is available for jointed goatgrass and feral rye.

Contact Drew Lyon at or 509-335-2961 for further information.

New Tool Helps Growers Identify Herbicide Mechanisms of Action

mayweed-1024x459-editedHerbicide resistant weeds are a growing concern in the Pacific Northwest, the US, and globally. One of the key tactics in the fight against herbicide resistant weeds is to alternate or combine herbicides with different modes of action; however, it is often difficult for growers to know what active ingredient(s) are in the jug they just bought and what mechanism(s) or mode(s) of action those active ingredients bring to the weed control effort.

There is a new tool available on the WSU Wheat and Small Grains website that allows growers to see what active ingredients are in the herbicides commonly used in wheat and barley production in Washington. The Herbicide Mechanisms of Action (MOA) 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 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. The tool also allows growers to search the database by active ingredient, mechanism of action group, or resistant weed.

By knowing what active ingredients and mechanisms of action they are using, growers can do a better job of managing weeds in a way that slows the likely development of herbicide resistance in their weed populations. This is extremely important as there have been no new mechanisms of action introduced into the market place in more than 20 years. It is unlikely that any new herbicide mechanisms of action will be available soon to replace current herbicides when they stop working.

Contact Drew Lyon ( or 509-335-2961) with your questions.

New ListServ Launched

subscribe-buttonThe Small Grain’s subscription service is now live! We understand that you are busy and don’t have the time to visit the
Wheat and Small Grains website every day to see if any new information has been posted. Now you don’t have to worry about missing new information that you are interested in.

Subscribe to the WSU Small Grains listserv to receive emails when new content is added to the site. You can customize what information you receive by choosing one or more categories to subscribe to.

The categories are:

  • Timely topics
  • Educational events
  • Variety selection
  • Soil and water
  • Diseases, insects, and weeds (all one category)
  • Marketing
  • Organic production
  • Other dryland crops (currently, legumes and oilseeds)

Simply give us your name and email, then you’ll be subscribed after you confirm your email!



Herbicide Resistance Has Been Around for 60 years

Photo courtesy of graduate student John Spring.

Photo courtesy of graduate student John Spring.

Glyphosate–resistant Russian-thistle was identified in Washington in 2015. Other weeds resistant to glyphosate have been identified in the state in recent years, including prickly lettuce, horseweed, kochia, and Italian ryegrass. Many people think that herbicide resistance is a recent phenomenon associated with the overuse of glyphosate-resistant crops, but as a recent article released by the Weed Science Society of America states, herbicide-resistant weeds predate glyphosate-resistant crops by 40 years.

The use of glyphosate-resistant crops (there are no glyphosate-resistant wheat varieties) is very limited in the dryland crop production systems of Eastern Washington and yet herbicide-resistant weeds are a growing concern for many Washington wheat farmers. Resistant weeds can evolve whenever a single approach to weed management is used repeatedly, whether that approach is chemical, mechanical, or cultural. A diverse, integrated approach to weed management is the first line of defense against herbicide-resistant weeds.

Washington wheat growers who suspect that they may have developed a weed that is resistant to an herbicide may want to submit a sample to the WSU Resistance Testing Program.

For questions contact Drew Lyon ( or 509-335-2961) or Ian Burke ( or 509-335-2858), who are Weed Scientists at Washington State University in Pullman.

Washington Ahead of Schedule, Again

The 2016 growing season is off to a fast and furious start in Washington.  Similar to 2015, the 2016 growing season is moving faster than average due to unusually warm temperatures.  This increase in heat units, or Growing Degree Days (GDD), impacts the rate at which plants develop and grow.  An increase in GDD corresponds to an increase in plant development.  GDD for wheat are calculated using a base temperature of 32°F.  To calculate GDD, subtract 32 from the average daily temperature.GDD Calculator

GDD = [(Daily Maximum Temp + Daily Minimum Temp)/2] – 32

For example, if your high temperature was 75°F and your low temperature was 45°F, you would accumulate 28 GDD for that day.

The Wheat and Small Grains website has the Wheat Grain Growing Degree Day Calculator, which will help users estimate current season GDD and compare them to recent years or the historical average.  The calculator is a collaboration with the AgWeatherNet program and operates based on data from the many AgWeatherNet weather stations around Washington.  You simply select the weather station nearest you, and a user-friendly graph displays GDD information.

Through April 2016, most wheat-growing areas of the state are 400-500 GDD ahead of the historical average.  That equates to wheat plants (and weeds) that are somewhere around two weeks ahead of average.  This faster growth has implications for management as it impacts the timing and efficacy of herbicide, fungicide, and fertilizer applications.  Remember to conduct your management practices based on plant development and not the calendar.  Also pay attention to pesticide labels for growth-stage restrictions and pre-harvest intervals.

Obviously, the weather can change dramatically between now and the middle of summer.  But as of right now, it appears that we may be on track for another early harvest.

New Publication on Prickly Lettuce Management in Wheat

The milky sap, or latex, of the plant could be used to produce rubber. (Photo by Jared Bell, WSU)

The milky sap, or latex, produced by the plant aids in  identification. (Photo by Jared Bell, former WSU graduate student.)

A new Pacific Northwest Extension publication, PNW688, Integrated Management of Prickly Lettuce in Wheat Production Systems, is now available. Prickly lettuce is a troublesome weed in wheat production systems throughout Eastern Washington. Individual plants can produce from 35 to 2,300 flowers and 700 to 46,000 seeds. Sanitation (the prevention of weed seed production and dispersal) is an important aspect of prickly lettuce management, as is growing a healthy, competitive wheat crop. Herbicides can provide effective control of prickly lettuce in wheat, but many biotypes are now resistant to ALS-inhibitor and synthetic auxin herbicides. An integrated management approach is required for the sustainable, long-term control of prickly lettuce.

Drew Lyon ( or 509-335-2961) and Ian Burke ( or 509-335-2858) are Weed Scientists at Washington State University in Pullman.


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