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Wheat & Small Grains Timely Topics

Proper Sprayer Cleanout Can Prevent Crop Injury

A stripe of peas that have herbicide injury.
The strip of winter peas in the middle of this picture were sprayed with Clethodim 2 EC, but the observed injury was from the previous products in the sprayer: Huskie + Osprey. A water rinse is never adequate when using a tank-cleaning herbicide like clethodim. This injury could have been avoided by carefully cleaning the sprayer before switching from spraying wheat to spraying peas.
The strip of winter peas in the middle of this picture were sprayed with Clethodim 2 EC, but the observed injury was from the previous products in the sprayer: Huskie + Osprey. A water rinse is never adequate when using a tank-cleaning herbicide like clethodim. This injury could have been avoided by carefully cleaning the sprayer before switching from spraying wheat to spraying peas.

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.

For questions, contact Drew Lyon (509-335-2961 or or Ian Burke (509-335-2858 or

New Bulletin Published on the Wheat Head Armyworm Complex

A newly published Extension Bulletin, PNW696, is titled “Integrated Pest Management for the Wheat Head Armyworm Complex in the Pacific Northwest.”

Since 2005, the wheat head armyworm has caused intermittent damage to wheat and barley crops in the PNW.

The two insect species found responsible were initially dubbed the “true” and “false” wheat head armyworms. As these species are closely related, we now refer to them as the wheat head armyworm complex (WHAC).

This publication covers identification, biology, and integrated pest management for WHAC. We emphasize pest monitoring and field scouting methods, and also discuss natural insecticides.

Authors are Diana Roberts, WSU Extension; Silvia I. Rondon, OSU Extension; Peter J. Landolt, USDA-ARS.

Don’t Worry About LMA and FN Yet

In 2016, Washington state wheat farmers experienced widespread problems with low Falling Numbers, for which we created our Grain Quality Resources page. The widespread low Falling Number issue was partly due to Late Maturity Alpha-Amylase (LMA) in response to wildly fluctuating temperatures about one month after pollen shedding. The high temperatures in the 90s on May 30 followed by high temperatures in the 60s has some farmers worried that we’re going to see a repeat of last year’s Falling Number fiasco. Such worries are premature because the wheat hasn’t yet reached the point where it is sensitive to fluctuating temperatures.

It is difficult to pinpoint the window of LMA-sensitivity for this year’s crop because it depends on when the wheat reached pollen-shedding, an event that depends on temperature and varies by variety. Wheat in central Washington reached pollen-shedding during the week following Memorial Day, while wheat further east is just starting to head.

Based on this, we guesstimate that wheat in central Washington may become LMA-sensitive during the last two weeks of June, while wheat further to the east may become LMA-sensitive within the first two weeks of July.

For questions or comments, contact Camille Steber, PhD, USDA-ARS, Molecular Geneticist, by email at or Ryan Higginbotham at

It’s Time to Scout for Blackleg in Winter Canola

If you haven’t already been walking your canola fields, now is the time, particularly after the very wet fall, warm temperatures right up to snow cover, and the extensive period of snow cover that added up to what can be perfect conditions for blackleg. In winter canola, look for lesions on primarily the lower leaves and leaf material that died back during the winter. The center of the lesions will have tiny black specks (pycnidia). Residue from previous canola crops and cover crops containing Brassica species should also be observed. Collect suspicious leaves, stems, and/or residues, and drop off or mail to WSU, UI, or OSU.

Here is a Blackleg in Canola FAQ document, and here for a blackleg update from WOCS.

Both documents include who to contact at WSU, OSU and UI for assistance.

Picnidia_blackleg P1010135_tn P1010151_tn

What A Difference A Year Makes

Nic Loyd; WSU AgWeatherNet Meteorologist;

If you have been wondering when warmer, late spring-like weather will finally arrive, you are probably not alone.  Temperatures in Washington have generally been near or below normal since December.  In fact, the 2016/2017 winter season (December to February) was central Washington’s coldest winter since 1984/1985.  However, it is important to note that the recent chill in early 2017 is only half of the story.  Although the cold 2016/2017 winter and the lack of prolonged springtime warmth so far this year may seem highly unusual, it is not, in a historical sense, as abnormal as one may suspect.  Much of the surprise of the early 2017 climate is related to the extreme warmth of the mid-2010s, as well as the suddenness of the pattern shift toward colder conditions that occurred in December 2016.  The interval from the spring of 2014 until November 2016 was one of unprecedented warmth for central/eastern Washington.  In fact, the temperature anomaly of central Washington’s two-year period from mid-2014 to mid-2016 (+3.9 deg) was almost double that of the now-second warmest (non-overlapping) biennium on record (+2.1 deg; 1990 to 1992).

The 2017 accumulated GDD (Growing Degree Days) total (base temperature 32 degrees F) for Pullman (through April 24) was 747 units, which is somewhat below the 2009-2016 average of 829 units.  However, the 2017 value is well below that of recent years (1081 and 1149 units in 2015 and 2016).  These numbers are illustrative of the fact that the perceived chill of 2017, though somewhat justified, is partly the result of the stark contrast with the remarkable warmth of the previous two years.

January 1 to April 24 Accumulated Growing Degree Days

Base Temperature 32˚F
Location 2017 Recent Avg Difference
Pullman 747 829 -82
Ritzville 710 893 -183
Fairfield 663 763 -100


For further GDD information, please see Growing Degree Day Calculator.

Given the volatility of our recent climate, one may reasonably wonder what weather regimes are anticipated for the near future.  Seasonal outlooks for later in 2017 suggest modest but appreciable odds that the state’s temperatures will again become generally warmer than normal.  Long range weather forecast models and decadal trends show an enhanced probability of above normal temperatures this summer, although abnormally cool waters in parts of the nearby Pacific Ocean act to slightly diminish those chances.  There is also a slight tilt toward abnormal dryness, although few clear signals exist regarding potential seasonal precipitation anomalies for the summer of 2017.

El Niño is a critical question mark going forward, and its ultimate strength/presence should significantly influence next winter’s climate pattern.  Unlike the weak La Niña conditions during the chilly 2016/2017 winter season, the notable potential for a weak to moderate El Niño augments the likelihood of a relatively warmer and drier winter of 2017/2018.  However, despite some indicators such as dynamical forecast models pointing strongly in that direction, other tools including historical analogs are more tempered about the eventual evolution of a robust El Niño event.  Therefore, its ultimate development later this year is favored but not yet certain.  Regardless of how Washington’s near-term climate patterns unfold, it seems likely that we can expect additional climatic surprises in the coming months and years.

For additional weather data and decision support information, please visit AgWeatherNet’s website.  To find weekly weather outlooks for Washington State, please select Outlook from the main page of the website, or visit the current outlook page.

For questions or comments, contact Nic Loyd by email at


Stripe Rust Update – April 2017

Dr. Xianming Chen, USDA-ARS Research Plant Pathologist in Pullman, and Dr. Mike Flowers, Oregon State University Extension Cereal Specialist, released disease updates (Dr. Chen’s update and Dr. Flower’s update) during the past week.

Not surprisingly, stripe rust has continued to develop on winter wheat across the region and is relatively easy to find.  Dr. Flowers reported finding stripe rust at variety testing locations near Dufur and Moro, OR, and in a commercial field near Moro. Dr. Chen reported finding actively sporulating stripe rust during the week of April 5 in over 80% of the approximately 70 fields checked in Adams, Benton, Columbia, Franklin, Garfield, Walla Walla, and Whitman Counties in WA, and Umatilla County in OR.

Stripe rust was most active near Walla Walla and Pendleton, where many fields have been sprayed with fungicide already. In other areas, rust ranged from 1 to 5% and is less severe than last year at this time due to lower temperatures. The Palouse in Whitman County is an exception, with stripe rust appearing about one month earlier than normal and similar to the severe epidemic years of 2011 and 2016.

Current weather forecasts continue to favor rust infection and spread, raising the potential for another severe stripe rust epidemic year. High-temperature adult-plant resistance (HTAP) has not kicked in yet and won’t become fully effective until nighttime/daytime temperatures are above 50°F/65°F.  Going forward, it will be important to continue scouting all winter wheat fields and consider using a fungicide with herbicide application if the variety is moderately susceptible or susceptible (rating 4 or greater in the Seed Buyers Guide) or active stripe rust is found on 2-5% of the plants in a field regardless of variety rating. Continue to monitor sprayed fields throughout the spring, especially near the end of fungicide effectiveness (3 to 4 weeks, depending on the fungicide).  For spring wheat, plant the most resistant variety available, preferably those rated 1 to 2.

Additional rust updates will be released as the growing season continues and conditions change. You can find additional information on stripe rust, including photos showing rust percentage, under Foliar Fungal Diseases in the Disease Resources section of the WSU Wheat and Small Grains website.

For questions or comments contact Tim Murray by email (, by phone (509) 335-7515, or Twitter (@WSUWheatDoc). For additional information contact Dr. Chen at or (509) 335-8086; or Mike Flowers at (541) 737-9940 or at

Proposed Rule Changes for Restricted Use Herbicides

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… » More ...
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