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Wheat & Small Grains Timely Topics – Weather Resources

Mild Winter Weather and Wheat Diseases – What to Expect?

Last year at this time, we were wondering whether winter was ever going to end. Remember the 60+ days of snow cover that began in early December 2016 and lasted into February 2017 and beyond?  In stark contrast, the winter of 2017-18 is turning out to be a no-show. It’s 50°F outside in Pullman today… » More ...

“Let’s Talk About AgWeatherNet” Podcast

A rainy sunset over the Palouse.
Episode 49 of Wheat All About It! features Washington State University's weather station system called AgWeatherNet. Join Scott Yates, director of Communications and Producer Relations for the Washington Grain Commission, in this episode titled, Let's Talk About AgWeatherNet. In this episode, he interviews head meteorologist, Nic Loyd, as they discuss the network's footprint in irrigated areas,… » More ...

The WSU Wheat Beat Podcast

Introducing the WSU Wheat Beat podcast, a new podcast brought to you by the WSU Extension Dryland Cropping Systems Team. Each week your host, Drew Lyon, will sit down with a WSU or USDA-ARS researcher to discuss the latest research related to small grains production systems in eastern Washington. Episode 1 will feature a discussion… » More ...

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


Slime Mold on Wheat

If you are seeing this in your wheat or straw stubble-don’t panic! These little yellow globs are slime molds. Slime molds are in the Myxomycota within the Kindgom Protozoa. These globs often get lumped together with fungi, but unlike fungi--which absorb their food--slime molds consume their food. The difference between slime molds and fungi is… » More ...

Recent Weather Could Affect Wheat Quality

As wheat harvest gets started in Washington, recent rainfall and cool temperatures have some growers worried about Mother Nature’s fickle ways with their crop.  Rainfall close to harvest can result in preharvest sprouting, which can negatively affect wheat quality.  Dr. Camille Steber, USDA-ARS plant geneticist, explains the potential effects of recent rains on this year’s wheat crop and what growers can do to manage this risk.

Fig. 1. Sponge cakes fall with increasing alpha-amylase from sprouting– image from WWQL, USDA-ARS, Pullman

The Hagberg-Perten Falling Number test is used to measure starch damage due to sprout.  Low FN is used as an indicator that grain contains a high level of alpha-amylase, an enzyme that degrades starch leading to poor end-use quality of wheat products (Figure 1).  Grain with an FN below 300 seconds is typically discounted in the Pacific Northwest.

Wheat that has been rained on is at risk of low FN.  Eastern Washington experienced periods of rainfall July 7 to 12, 2016, just as winter wheat harvest approached.  Chances are, buyers will check FN to protect themselves from sprout damage risk.  Whether or not your grain is likely to have low FN problems depends on the susceptibility of the cultivar you grew, on the local weather, and the timing of the rain relative to maturity date.

Fig. 2. The chances that rain will induce sprouting and low FN increase the longer the wheat “after-ripens” or sits dry on the mother plant after the wheat turns matures (turns yellow). Thus, dormancy and sprouting tolerance are lost as the wheat stands in the field.
Fig. 2. The chances that rain will induce sprouting and low FN increase the longer the wheat “after-ripens” or sits dry on the mother plant after the wheat turns matures (turns yellow). Thus, dormancy and sprouting tolerance are lost as the wheat stands in the field.

Preharvest sprouting is the initiation of grain germination while still on the mother plant.  Germinating seeds degrade starch for use in fueling growth.  Lack of seed dormancy explains 60-80% of genetic sprout susceptibility.  Dormant grains can’t germinate, and so don’t suffer sprout damage in the rain.  Seed dormancy is strongest at maturity, just as the wheat turns from green to yellow.  Dormancy is lost gradually over time as the dry, mature grain “after-ripens” (Figure 2).  Winter wheat that still had some green color is less likely to have a low FN due to sprouting than wheat that was completely yellow and dry when it rained.  Since green grain cannot sprout, spring wheat that was green when it rained should be safe from low FN, as long as there isn’t another ill-timed rain event.

Not all rainstorms induce sprouting.  Seed dormancy is broken by cool, rainy conditions.  So if the temperatures are in the 80s °F when it rains, the wheat is less likely to sprout than if the temperatures are in the 60s.  Low FN is also more likely when there are multiple rainy days in a row, as the wheat stays wet longer.

How do you spot sprouted grain?

Fig. 3. A sprouted grain with a seedling root just poking out of the grain is not obviously germinated, but has low FN/high amylase.
Fig. 3. A sprouted grain with a seedling root just poking out of the grain is not obviously germinated, but has low FN/high amylase.

It takes a lot of rainfall to make a seedling sprout out from a wheat spike (about 3 days of constant rain at 70 degrees).  If you look closely at a mildly sprouted grain, you can sometimes see a small root protruding from the germ-end (Figure 3).  Such grain can have a very low FN (under 200 sec).  As the sprouted grain dries, the root can shrink back into the grain leaving behind a small crack at the embryo end.  Sometimes this cracked end breaks, leaving behind a germ-less grain.  So get out your magnifying glass.

Low FN (200-300 sec) can also be caused by late-maturity alpha-amylase (LMA) induced by heat shock or cold shock during grain maturation.  LMA causes low FN in grain that appears to be sound. We had some big temperature fluctuations this summer, so there may be some lower FN in wheat that saw no rain.  Some LMA-susceptible suspects include SY-Ovation, Bruehl, Jasper, and Alturas.

Plant cultivars with genetic resistance to sprouting and LMA.  We can use past preharvest sprouting events to judge which cultivars have more genetic resistance to sprouting.  For example, there were major sprouting events in Fairfield, Lamont, Pullman, and other locations in 2013.  The FN of all cultivars grown in the WSU Cereal Variety Trial at all locations in 2013 and 2014 can be found on the Project 7599 PNW Falling Number website.  One problem is that many of the highly PHS tolerant cultivars such as Mary and Masami are older cultivars that may not compare well to recent cultivars for yield and disease resistance.  The falling number versus yield tool on the Project 7599 website can help you take both yield and FN into account when choosing a cultivar (  Examples of sprouting-resistant cultivars include Puma, Skiles, Coda, and Bobtail.  Sprouting-susceptible cultivars include Bruehl, Xerpha, AP-Legacy, LWW10-1018, and Bruneau.  Ongoing research will improve sprouting resistant choices.

Harvest wheat quickly after maturity to reduce risk of getting rained on.  Wait for the rained-on wheat to dry well before harvesting to avoid germination in the truck.  Also, avoid harvesting green wheat, as green kernels have higher alpha-amylase (lower FN) than mature grain.  Green kernels can be a problem if you combine wheat that is yellow on the hill with green wheat from the draw.

Avoid mixing likely-sprouted grain with likely-unsprouted grain.  A little bit of alpha-amylase can cause big FN problems.  Mixing equal amounts of FN 200 grain with FN 400 grain will not give you a load at FN 300 sec.  Instead you will end up with something well below 300.  If you have one field that was greenish and another field that was fully yellow when it rained, you might make more money if you keep them separated when you sell.  The same is true if you planted both a sprouting-resistant and susceptible cultivar in separate fields.
Store mildly sprouted grain.  Some research suggests that alpha-amylase levels drop during storage – it could be that UV light or heat degrades the enzyme over time.  If the FN is moderately low (200-300 sec), it might help to store grain for 2 to 3 months to see if the FN rises.  If the FN is very low, storing the grain won’t reverse starch damage that has already occurred.  So storing the grain may not greatly improve its value.

If you want to read more about the Falling Number test and sprout damage, see:
“Preventing those Falling Numbers Blues” – Wheat Life  (
“Falling Numbers: research strategies to stay out of the red.” – Wheat Life (
2013 and 2014 Falling Number Data (

Camille Steber is a molecular geneticist with the USDA-ARS in Pullman, WA. For questions/comments, contact her at or 509-335-2887.

How to Calculate Growing Degree Days

You can calculate Fahrenheit Growing Degree Days (F-GDD) from weather data on the internet.

  • Visit If a page will not load, try refreshing it. 
  • Click on Map Index. This will bring you to an interactive map of the U.S.
  • Click on your state. A pop-up box will appear showing interfaces available.
  • In individual networks, select METAR, a NOAA site.  Now you will see the Heading, “Degree-day and Phenology Model Calculator.”
  • The first task is “Select Model”.  Hit the down-arrow on this bar and go to the bottom of the drop-down list to “winter wheat Karow et al 1993” and select that.
  • Next set the lower threshold to 32 and the upper threshold to 130.  Ignore the box asking for Calc. method.
  • Now enter your start (planting) date or, if you dusted the crop in, enter the date of the first significant rain after planting.
  • Then enter end date, for example: Sept. 25, Nov. 11.  Depending on your date choices select same year or following year.
  • Ignore the boxes asking for Forecast zip code and Calc. selection.
  • Now go down into the table and find a weather station near you, then in that line, select the correct year and, if needed, hit “CALC.”
  • Cumulative F-GDD will be shown in tabular form with plant milestones.

For more information contact Tami Johlke, USDA-ARS Biological Research Technician.

Washington State University