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This page is intended to assist farmers and crop consultants who wish to cooperate in providing stem canker survey data for the Row Crops Pathology project at the Plant Science Department at South Dakota State University. We thank you for your willingness to assist us in gathering accurate survey information that will help us understand how widespread and damaging stem canker is becoming on soybeans in South Dakota. This research project is funded in part by the South Dakota Soybean Research & Promotion Council.
Information and data we are seeking include: field location and legal description, owner/grower, variety and seed source, estimate of incidence (percent infection), acres infected, field characteristics and history including tillage, rotation, planting pattern., soil type. Data may be sent via e-mail or phoned into any of the Row Crops Pathology personnel listed at the bottom of the page.
Contact information is shown at the bottom of the page.
Stem canker is a mid- to late-season disease of soybeans caused by the fungus Diaporthe phaseolorum. In our experience it usually becomes noticeable in fields about mid-August on through to maturation of the soybean crop in late September. It can still be detected in fields following maturity because of the tendency of infected plants to retain leaves. There are two forms of the disease, Northern Stem Canker and Southern Stem Canker. Both diseases have very similar symptoms and may not be distinguishable from each other in the field to the untrained observer. The differentiation between the two diseases is based on which variety of the fungus is the causal pathogen. Northern Stem Canker is caused by D. phaseolorum var. caulivora (DPC) and Southern Stem Canker is caused by D. phaseolorum var. meridionalis (DPM). In South Dakota, we are dealing with Northern Stem Canker (NSC). We have not identified any isolates of DPM in our surveys to date. Identification of our isolates has been based on well-established molecular techniques (polymerase chain reaction or PCR) as well as morphology of isolates in pure culture.
Northern stem canker caused severe losses in the Midwestern and North Central Regions of the United States and Ontario, Canada in the late 1940's and early 1950's, but became insignificant as a problem when extremely susceptible varieties were removed from production. Southern stem canker arose as a problem in the southern United States in the 1970's and continues to be significant problem for southern soybean farmers. The resurgence of stem canker in the past few years in our region may be related to the deployment of highly susceptible varieties, changes in agronomic practices, changes in the pathogen population, as well as seed sources. The factors that allow NSC to become epidemic in any given soybean field are unknown and present a challenging research problem. Elucidating the host, pathogen and environmental factors contributing to stem canker epidemics in South Dakota is one of the main research topics for the SDSU Row Crops Pathology Project.
 | Field near Vienna, South Dakota on September 10, 2001. There is a low incidence of stem canker in this field, probably less than 1 -5%. Dead plants (some examples are pointed out by red arrows) were killed by girdling stem canker lesions. Symptoms are conspicuous from early to mid-August through maturation in South Dakota.
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 | Field near Hayti, SD on August 30, 2000. Disease incidence in this field was 30-40%. |
 | Field near Brookings, SD on September 1, 2005. Disease incidence in his field was 40 -50% throughout. The crop in the previous year was corn in this part of the field. In the other section of the field, which was equally affected, the crop was preceeded by three years of alfalfa.
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Symptoms include cankers or discolored areas centered on lower leaf nodes (photos 4 & 5), dead and dying petioles, rapid wilting resulting in shriveled gray to brown colored leaves (photo 6). Canker appearance is quite variable ( photo 4.). On susceptible cultivars, cankers "run" and are diffuse and not well defined (photo 4, compare stems). If cankers girdle stems, then plants are killed.. In some cases cankers are more limited (photo 4).
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Two soybean diseases that may be confused with stem canker are White Mold (Sclerotinia stem rot) and Phytophthora Root & Stem Rot (PRR). Absence of sclerotia on and in stems and 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, wilting characteristics and distribution within fields. Developing stem canker lesions are found low on the main stem. usually the V2 - V5 nodes, but PRR lesions are found on the base of the stem and are continuous with the soil line.
Project Leader - Dr. Thomas Chase Phone: 605-688-5550 FAX: 605-688-4024 E-mail: thomas_chase@sdstate.edu |
Project Technician - Richard Geppert Phone: 605-688-6246 FAX: 605-688-4024 E-mail: Richard.Geppert@sdstate.edu |
Secretary: Cindy Olson Phone: 605-688-5156 FAX: 605-688-4024 E-mail: lucinda_olson@sdstate.edu |