Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Early Misdiagnosed Stem Canker Poses Risk for Soybean Growers

Something didn’t look right in the soybean field on the north side of the road. It was the wilted look of those leaves turned bottom up to the sun that made SDSU plant pathologist Thomas Chase pull over and stop that day in early September 2009.

Though it had the look of some more familiar late season soybean diseases, it reminded Chase of a disease he’s seen increasingly since the late 1990s: stem canker. At least in some locations, it will again be a problem in 2010.

“When we first started finding stem canker in South Dakota, it was kind of a surprise. I didn’t even have it on my radar screen. I didn’t even teach it in my class, hardly. Then in about 1998, we started getting fields that were just hammered with stem canker,” Chase recalled.

“We had these growers calling us up and saying, ‘I think my crop’s maturing early. I’m not sure what’s going on.’ We went out there and found that 50 percent of the plants were hit with stem canker. Yes, they were maturing, because they were getting killed — they had a pathogen that was causing a disease.”

On that September day in northeastern South Dakota, Chase’s windshield hunch made him suspect the same problem. He found dead plants scattered through one corner of the field in only a few minutes of scouting. And then the telltale sign he was looking for — a plant that shows an area of reddish brown to black girdling the stem. It’s that zone of dead tissue that is called a canker — essentially a roadblock for water and nutrients trying to zip from the root of the plant to the leaves.

Stem canker is caused by a fungus — or more accurately, two different pathogenic varieties of the fungus Diaporthe phaseolorum. The disease is divided into Northern stem canker and Southern stem canker types. Northern stem canker is caused by D. phaseolorum var. caulivora (DPC) and Southern stem canker is caused by D. phaseolorum var. meridionalis (DPM). At this point, only the Northern stem canker has been found in South Dakota.

Northern stem canker caused severe losses in the Midwestern and North Central Regions of the United States and Ontario, Canada in the late 1940s and early 1950s. Once growers removed extremely susceptible varieties from production, it became insignificant as a problem.

Southern stem canker arose in the southern United States in the 1970s and continues to be significant problem for southern soybean farmers.

The resurgence of stem canker in the past few years in northern states may be related to the deployment of highly susceptible varieties, changes in farm practices, changes in the pathogen population. It may also have to do with seed sources, Chase said.

Scientists don’t fully understand the circumstances that allow Northern stem canker to thrive. Figuring out how host, pathogen and environmental factors contribute to stem canker epidemics in South Dakota and the surrounding region is one of the main research topics for the SDSU Row Crops Pathology Project.

At least so far, Northern stem canker’s impact has been scattered and intermittent. The loss to the grower depends on how many stems get infected and how quickly it kills them.

“It’s been so intermittent and dispersed that we have to have the growers let us know where it’s happening,” Chase said. “But I think we may be building up to a year that’s going to be just perfect, and we’ll have a more widespread epidemic.”

At least on a field-by-field basis, the disease can take a heavy toll. Chase’s hunch on his early September scouting trip was that the field he had found was in trouble, and he was right. When he returned to check the field in mid-September, he found 90 percent of the plants had stem canker in a field that had been seeded to a mixture of alfalfa and intermediate wheat grass for more than a decade.

“In other words, the field hadn’t seen soybeans for 11 years,” Chase said. “We will continue to do research on the field, including doing soil assays for the pathogen as well as assaying old alfalfa and wheat grass residues and testing alfalfa for susceptibility to the pathogen.”

Chase learned afterward from the farmer working that field that his average yield for the plot in 2009 was 15 bushels an acre, whereas in a normal year he would have expected at least 40 bushels an acre.

Management tips
Here is Chase’s advice to growers during the 2010 season:
Start serious scouting for stem canker in early to mid-August and look for symptoms that include cankers or discolored areas centered on lower leaf nodes, dead and dying petioles, rapid wilting resulting in shriveled gray to brown colored leaves. Canker appearance is quite variable. On susceptible cultivars, cankers “run” and are diffuse and not well defined. If cankers girdle stems, the plants die. In some cases cankers are more limited, meaning there is less early wilting and yield loss.

Two soybean diseases that may be confused with stem canker are white mold (Sclerotinia stem rot) and Phytophthora root and stem rot (PRR). Absence of sclerotia on and in stems and absence of white moldy growth, shredded stems and bleached/tan lesions would rule out white mold.

PRR can be ruled out by location of stem lesions, as PRR lesions are found on the base of the stem and are continuous with the soil line. Developing stem canker lesions are found low on the main stem, usually the V2 to V5 nodes. In addition, the distinctive appearance of rapidly wilted leaves and widespread but even distribution within fields — sometimes an entire field or large sections of a field — are more typical of stem canker than of PRR.

Management advice is scanty for growers once Northern stem canker is confirmed in a field.

“We would probably suggest rotating out of soybean for several years in fields that have a history of NSC. Growers should also probably try to obtain a variety with a higher level of resistance if they can and consider using fungicide-treated seed,” Chase said. “At this stage it’s important for growers to understand that they may have a different disease problem than white mold or PRR, and they don't want to apply a management strategy based on a misdiagnosis.”

For more information, read Chase’s article about northern stem canker at the North Central Soybean Research Program’s Plant Health Initiative at this Web link:

Find additional images to help in scouting for stem canker by referring to Chase’s row crops pathology Web page,

Chase’s work is partially funded through what was formerly the Cooperative State Research, Education, and Extension Service, or CSREES, now the National Institute of Food and Agriculture; and by the South Dakota Agricultural Experiment Station. Additional funding is provided by grants from the South Dakota Soybean Research & Promotion Council.

Thomas Chase | Newswise Science News
Further information:

More articles from Agricultural and Forestry Science:

nachricht Forest Management Yields Higher Productivity through Biodiversity
14.10.2016 | Technische Universität München

nachricht Farming with forests
23.09.2016 | University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES)

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

First results of NSTX-U research operations

26.10.2016 | Physics and Astronomy

UCI and NASA document accelerated glacier melting in West Antarctica

26.10.2016 | Earth Sciences

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

More VideoLinks >>>