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Wheat & Small Grains Timely Topics

Metalaxyl-resistant Pythium

Metalaxyl is the active ingredient in fungicides such as Ridomil, Apron, Subdue, and others used to prevent root rots and seedling diseases caused by the fungus-like organism Pythium. Called Oomycetes, these fungus-like organisms require water for a portion of their life cycle, because most produce a swimming spore and are more closely related to brown algae than to true fungi like stripe rust. Other common oomycetes are the downy mildew and the late blight pathogen on potato. Pythium is a soilborne pathogen present in most agricultural soils that is able to attack a diversity of crops grown in the PNW including wheat, chickpeas (Chen and Van Vleet, 2016), lentils, canola, potatoes (Porter, et. al, 2009), other vegetables, and even the tree fruit. Because Pythium is not a true fungus, only certain fungicides can be used to protect a crop with, metalaxyl being most frequently used, most often in the form of a seed treatment. Unfortunately, in both potato-producing regions and in chickpea production in the Palouse, metalaxyl-resistant Pythium have been found. These resistant Pythium species are able to cause damping-off, stand and crop loss, and leak (in potatoes) despite the seed treatments. The fungicide ethaboxam is proposed as an alternative for managing metalaxyl resistant Pythium populations. As metalaxyl is our main weapon against Pythium and other oomycetes, it is vital that we be aware of developing resistance so that we can manage these populations and slow further development. Changes in management practices that encourage the rapid growth of seedlings and reduces cool, wet soil conditions until plants are robust enough to withstand minor damage can also help reduce the impact of Pythium.

If you suspect that you may have metalaxyl resistant Pythium, you are encouraged to submit a soil or plant sample to the Plant Pest Diagnostic Clinic in Pullman for testing.


For more information:

Weidong Chen and Steve Van Vleet. Chickpea damping-of due to metalaxyl-resistant Pythium: an emerging disease in the Palouse. 2016. http://hdl.handle.net/2376/6273

Reference:

Cook, R.J. and B.X. Zhang. 1985. Degrees of sensitivity to metalaxyl within the Pythium spp. pathogenic to wheat in the Pacific Northwest. Plant Disease 69: 686-688.

Porter, L.D., P.B. Hamm, N.L. David, S.L. Gieck, J.S. Miller, B. Gundersen, and D.A. Inglis. 2009. Metalaxyl-M-resistant Pythium species in potato production area of the Pacific Northwest of the U.S.A. American Journal of Potato Research 86: 315-326.

Variable Rate Nitrogen Application – A Grower’s Perspective

The unique, hilly topography of the inland Pacific Northwest causes great within-field variability in soil and water conditions. As a result, crop yield potential and crop response to nitrogen (N) applications will vary according to the hillslope position, steepness, and aspect of any planted location. Thus, variable rate N (VRN) application makes sense for growers in this region.

In a recently published case study, Variable Rate Nitrogen Application: Eric Odberg, a grower from Genesee, Idaho, shares his 10 years of experience using VRN application in a direct seeding (no-till) system. Although transitioning to VRN application is a big decision with many challenges along the way, Eric’s 10 years of experience has brought him numerous benefits. These benefits include reduced fertilizer input, reduced lodging, reduced risk of N losses to the environment, and increased financial gain. Furthermore, because Eric complements VRN application with direct seeding and diversified crop rotations, his farm’s soil quality has also improved.


For questions or comments, contact Georgine Yorgey (yorgey@wsu.edu) or Sylvia Kantor by email at kantors@wsu.edu at the Center for Sustaining Agriculture and Nature Resources, Washington State University, or Kathleen Painter by email at kpainter@uidaho.edu at the Department of Agricultural Economics and Rural Sociology, University of Idaho.

Concern Over Snow Mold of Wheat in Eastern Washington

The winter of 2016-17 has been unusually long compared to the past few years, and the prolonged snow cover has raised concerns over potential for snow mold development in eastern Washington. On the Waterville Plateau in Douglas County where snow mold of wheat has been a chronic occurrence since the 1940s, snow has been on… » More ...

A Win-Win: Building Soil Health While Gaining Yield & Profit

A 375-horsepower crawler tractor pulls a 1,000-gallon tank cart and a 32-foot-wide undercutter implement during primary spring tillage plus nitrogen and sulfur fertilizer injection in May. The undercutter’s narrow­-pitched and overlapping wide V-blades slice beneath the soil at a depth of five inches to completely sever capillary channels and halt the upward movement of liquid water to retain seed-zone water in summer fallow for late-summer planting of winter wheat. Most of the winter wheat residue from the previous crop is retained on the surface to control wind erosion.

Soil health and soil quality are two synonymous terms that are defined interchangeably by the Natural Resources Conservation Service (NRCS) as follows: “Soil health, also referred to as soil quality, is the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”. As a complicated bioecological system, soil is a living system with an abundance of diverse bacteria, fungi, and other microbes that have significant effects on soil physical and biological properties. Healthy soils provide a healthy physical, chemical, and biological environment for optimal crop growth.

Inherent soil properties that contribute to soil health, such as soil texture, are determined by the natural parent material and the environmental conditions during soil formation, in the absence of human impacts. Soil health is dynamic, rather than static, and can be degraded or improved with time as a result of soil use and management by humans. Soil degradation causes soil organic matter, fertility, structure, and biodiversity to decline and soil acidification to increase. As a result, crop productivity can decrease, crop diseases and weed problems can increase, and environmental quality can suffer.

Building soil health is becoming increasingly important worldwide. Soil imbalances in essential crop nutrients can be addressed by applying fertilizer and organic amendments. And soil chemical, physical, and biological properties can be significantly improved by adopting management practices such as no-tillage or reduced tillage.

A recently published article, Best Management Practices for Summer Fallow in the World’s Driest Rainfed Wheat Region, compares the effects of three fallow management practices on soil water dynamics, wheat stand establishment, grain yield, and economic returns. This research was conducted on two farms in the driest rainfed wheat production region in Washington (WA). At the drier site, results from the 5-year study indicated that late-planted winter wheat on no-tillage fallow was as profitable as on tilled fallow. Additionally, the study found that, at the slightly wetter site, undercutter tillage resulted in equal or greater grain yield compared with both traditional tillage and no-tillage.

Another recently published article, Wheat Farmers Adopt the Undercutter Fallow Method to Reduce Wind Erosion and Sustain Profits, surveyed 47 farmers who had been practicing undercutter tillage for several years. Farms were located in the low-rainfall (< 12 inches annually) zone of east-central WA and north-central Oregon (OR). Interviewers asked farmers to compare the agronomic and economic performance between undercutter tillage and conventional tillage. Results of this survey concluded that, on average, undercutter and conventional tillage systems have equal profitability. However, the undercutter system offers a costless air quality gain and a soil health benefit in terms of reducing wind erosion.


For questions or comments, contact Dr. Douglas L. Young (dlyoung@wsu.edu), Professor, in the School of Economic Sciences, or Dr. Bill Schillinger (William.schillinger@wsu.edu), Professor, in the Department of Crop and Soil Sciences at the Washington State University.

 

Adjusting Wheat-Based Management Strategies for Oilseed Production

Field of canola.

Oilseeds, such as canola, are recognized as rotational crops that can benefit the agro-ecological and social-ecological systems within the traditional wheat-based cropping region of the inland Northwest Pacific. Although farmers can continue to use wheat-based farm equipment, management practices need to be adjusted specifically to canola physiology and morphology to optimize yield and quality.

A recently published article, Physiology Matters: Adjusting Wheat-Based Management Strategies for Oilseed Production, compares the physiological and morphological characteristics between wheat and oilseeds. Characteristics studied included the differences in seed size, shoot meristem, cold tolerance, and above and below ground morphology. Based on these differences, the article provides recommendations for modifying wheat management strategies, for example, planting date and fertility management, for canola production.


For questions or comments, contact Dr. William Pan at wlpan@wsu.edu or Karen Sowers at ksowers@wsu.edu.

First Stripe Rust Update of the 2017 Season – January 2017

As many of you know, the 2016 crop season was very favorable for stripe rust due to the mild winter and early spring with temperature and moisture conditions that were favorable for rust development. In some cases, this resulted in severe rust in fields planted to susceptible varieties and/or multiple fungicide applications to limit rust… » More ...

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 icburke@wsu.edu or 509-335-2858.

New Publication Addresses Acidic Soils and How They Interact with Root Diseases

As soil acidification continues to be a concern for growers in the Pacific Northwest, WSU researchers are working to provide information and recommendations for how to mitigate adverse effects. Root diseases are one of many factors influenced by acid soils, depending on the soilborne pathogen. The new publication, Acid Soils: How Do They Interact with Root Diseases?, explains how soil pH affects root diseases and also offers examples of common ones in the Pacific Northwest.

Cereal growers in the Pacific Northwest have been experiencing an increase in soil acidity (lower pH) primarily due to a long history of ammonium fertilizer use.

In eastern Washington and northern Idaho, soil acidification tends to be worse in areas that are annually cropped, do not include nitrogen-fixing legumes in the crop rotation, and in areas that were historically forested. Forested soils tend to have a lower pH buffering capacity, making them more prone to shifts in soil pH. These same areas also typically include more forage and seed grass production and seldom include legumes in rotation, meaning that there is more intensive nitrogen application to the soil.

In addition, direct seeding can result in a stratification of soil pH in which the top few inches of soil are more acidic. This is because acidification caused by fertilizer application in the top soil layers is not diluted by mixing with the more alkaline soil below the fertilizer zone. However, the contribution of this stratification on management of soil acidity in direct-seed systems has not been evaluated.


For questions or comments, contact Tim Paulitz at USDA-ARS Wheat Health, Genetics and Quality Research Unit (paulitz@wsu.edu or timothy.paulitz@ars.usda.gov) or Kurtis Schroeder, Assistant Professor in the Department of Plant, Soil, and Entomological Sciences at the University of Idaho (kscroeder@uidaho.edu).

Washington State University