We have received a number of phone calls recently concerning crop damage in peas treated with herbicides containing the active ingredient clethodim. Clethodim is an ACCase inhibitor (Group 1) used to control grass weeds in broadleaf crops. There is no clethodim activity on broadleaf crops like peas. So why is there sometimes injury to peas?
Clethodim products containing 26.4% or 2 pounds of clethodim per gallon (for example, Arrow 2 EC, Clethodim 2 EC, and Select 2 EC) contain as much as 70% petroleum distillates. This high level of petroleum distillates, combined with the required crop oil concentrate and liquid fertilizer additives, can act as a sprayer cleaner, dislodging old herbicide residues that are embedded in tank walls or hoses, resulting in unwanted herbicide residue in the sprayer liquid. It is these residues, and not the clethodim, that are injuring the peas.
This type of damage, which is not unique to clethodim products, can be avoided by properly cleaning sprayers between applications, particularly when changing what crop is being treated. While proper sprayer cleanouts are time-consuming, it can save a lot of money and misery. Removing Herbicide Residues from Agricultural Application Equipment is an excellent publication by Purdue Extension that can help you do a good job of sprayer cleanout and possibly save you headaches and dollars down the road.
Consider yourself very lucky if you have not had to deal with mayweed chamomile, a.k.a., dog fennel, in your wheat or pulse crops! Mayweed chamomile is a troublesome weed in small grain and pulse crops throughout the high rainfall zones of the Inland Pacific Northwest. It is an annual that can germinate in the fall or spring and that reproduces only by seed. Individual plants can produce as many as 17,000 seeds, and seed remain viable in the soil for many years. Preventing seed production is the key to managing mayweed chamomile! While herbicides are an effective tool for mayweed chamomile control, herbicide-resistant biotypes are an increasing concern. The new Extension publication PNW695 ‘Integrated Management of Mayweed Chamomile in Wheat and Pulse Crop Production Systems’ is now available on the Wheat and Small Grains website. This publication will help growers and crop consultants develop an integrated program for the management of this prolific weed in wheat and pulse crop production.
For questions or comments, contact Drew Lyon at firstname.lastname@example.org or by phone at 509-335-2961.
The Washington State Department of Agriculture is considering rule changes affecting the use of restricted use herbicides. The possible rule changes were agreed upon by a workgroup consisting of various agricultural sector representatives and representatives from WSU. The existing rules covering restricted use pesticides are extensive, complex, and confusing. For example, there are over 50 different established Areas in eastern Washington, each with their own restrictions. Some of the existing rules are over 50 years old and lack relevancy in today’s agriculture. For example, current rules require nozzles with a minimum orifice diameter, but current nozzle manufacturers and pesticide labels refer to the size droplet spectrum produced by a particular nozzle type at a specific pressure. The current rules also limit spray pressures below that needed by modern nozzle types such as air induction nozzles. The purpose of the proposed changes is primarily to repeal redundant and very outdated rules. The proposed new rules do not impose any additional regulatory requirements and the Department does not believe the changes will pose any increased risk to sensitive crops. The Department is seeking public comment on the proposed rule changes before filing an official rule-making proposal sometime in the fall of 2017.
The Department is considering the following changes:
- Amending nozzle and pressure requirements in the three WAC chapters to reflect current standards that applications must be made by creating a droplet spectrum size (e.g., medium, coarse or very coarse) that is in conformance with ASABE (American Society of Agricultural and Biological Engineers) standards;
- Repealing the 85 degree Fahrenheit cut-off requirement in individual county rules since it is in the statewide rule (redundant);
- Repealing maximum wind speed restrictions in individual county rules and adding a maximum 15 mph wind speed restriction to the statewide rules;
- Repealing restriction in statewide rules that limits the addition of oil carriers and adjuvants to one pint per acre;
- Repealing restrictions in individual county rules that prohibit use of oil type carriers for brush control during certain times of the year;
- Repealing restriction in statewide rules that prohibits mixing, loading and equipment decontamination (also aircraft takeoff and landing) in a manner that causes damage to susceptible crops;
- Repealing restrictions in counties and specific “Areas” of counties that limit mixing loading of aircraft to formulations that can be applied in the Area where the airstrip is located;
- Repealing the prohibition in statewide rules on turning or flying low over cities, towns, residences and other sensitive sites;
- Repealing the prohibition in the statewide rules for storing use-restricted herbicides in “Areas” where their use is prohibited unless they are in a sealed container and the outside of the container is not contaminated; and
- Repealing the provision in the statewide rules that indicates application of use-restricted herbicides through irrigation is subject to the same requirements as ground applications except for nozzle size and pressure requirements.
The Preproposal Statement of Inquiry provides details on how interested parties can provide comments on the proposed rule changes to the Washington State Department of Agriculture. The Explanation of Possible Rule Changes explains the proposed rule changes and why the changes are deemed beneficial. This is a good faith effort to simplify and update rules related to the application of restricted use herbicides. Please consider providing your thoughts on the proposed rule changes to the Washington State Department of Agriculture.
For questions, contact Drew Lyon by phone at 509-335-2961 or by email at email@example.com.
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 firstname.lastname@example.org or 509-335-2961.
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 email@example.com or 509-335-2858.
Earlier this year we introduced a handy calculator that uses data from a standard 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.
Weeds 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 (firstname.lastname@example.org or 509-335-2961) with your questions or suggestions for improvement.
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 email@example.com or 509-335-2961 for further information.
Herbicide 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 (firstname.lastname@example.org or 509-335-2961) with your questions.
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