Updated September 5, 2024:
Minnesota Soybean Research and Promotion Council
Research Progress Report
August 30, 2024
Project Title: Addressing Management Challenges with Soybean Stem Diseases in Minnesota
Principal Investigator(s): Dean Malvick
Project Period Ending August 31, 2024
Research Question/Objectives: This project focuses on the priority area of soybean pest management. It centers on research into managing against yield and quality limiting effects of stem rots. Stem diseases are widespread and problematic across Minnesota. They often clearly damage plants and yield, but also go undetected and cause yield losses. Understanding how to manage soybean stem diseases more effectively could potentially result in yield increases in many areas. This project targets management strategies for the diseases brown stem rot (BSR) and pod and stem blight (PSB). BSR is a common and important soybean disease in Minnesota. Crop rotations and resistant varieties can suppress BSR, however, neither method is a complete solution to managing the disease. Because BSR is a continuing problem for soybean production in Minnesota, more information is needed to understand risk factors and disease management options. The BSR pathogen (Cadophora gregata) is reported to only infect soybean, adzuki bean, and mung bean, but the host range is poorly documented and understood; and the efficacy of seed treatment fungicides for managing BSR is unknown. Pod and stem blight is also a common and problematic disease in Minnesota soybean fields and causes more damage and yield loss than is recognized. Soybean varieties vary in resistance to PSB and crop rotation may be beneficial, but this disease and the best methods to manage it are poorly understood. In summary, this project is addressing short and long-term goals to manage two common and damaging soybean stem diseases: brown stem rot (BSR) and pod and stem blight (PSB).
Project Updates for this period:
Objective one, focused on brown stem rot.
• Field and greenhouse studies are underway to determine if any of the common seed treatments are effective against BSR or the causal pathogen. Field studies were established in Waseca and Rosemount with different seed treatments in May 2024. The studies have been progressing well throughout the summer. Crop development is 1-2 weeks behind normal in those studies, and we expect BSR to develop and the plants to be ready for evaluation in the first 2-3 weeks in September. Thus, we do not have results yet from the field studies. Lab and growth chamber studies for fungicide efficacy have been proceeding throughout the summer, and the preliminary results from suggest that some fungicides have suppressive effects on the BSR pathogen, although the effective concentration may be higher than the typical doses used to treat seeds. More testing and analysis will be done in the next project period to develop more solid and conclusive results. The studies in the growth chamber are also underway and will be completed later in the fall.
•The host range of the BSR pathogens is unknown, which could have implications for management of BSR with crop rotation. Twenty-seven crop and weed species were evaluated in greenhouse experiments to determine if they can serve as hosts of the BSR pathogen. Although the final analysis of those plants and results is continuing, initial results confirm that mung bean is a host, and suggest that some edible bean (Phaseolus vulgaris) varieties may also be hosts of C. gregata. Final testing and analysis of the plant samples will be completed this fall to confirm these results and to determine if other plants are hosts of the BSR pathogen.
•Our work to develop and validate an improved and higher throughput method to evaluate soybean lines and varieties for resistance to BSR has provided additional results. Initial results suggest that it may be feasible to evaluate resistance within a month after planting in a greenhouse vs 2 months. Additional experiments have been conducted using two different lab testing methods, and data are still being obtained and analyzed. Experiments will continue into the fall and winter. The initial results suggest that this method based on quantity of the pathogen in soybean stems, could potentially reduce cost, time, and challenges with evaluating resistance to BSR caused by both types of the BSR pathogen.
Objective two, focused on pod and stem blight.
•This project period focused on additional field and greenhouse studies to study development and management of pod and stem blight of soybean. One large experiment was completed in the greenhouse, but for reasons unknown very little developed following the use of the same methods and check varieties as used previously. Fluctuating greenhouse temperatures in the summer may have suppressed disease development. Another experiment was started in the greenhouse in mid-August. Field studies are also underway. Plants were inoculated using two methods in field studies in St Paul. Like BSR in the field studies, it is too early for full disease development and evaluation of the plots and plants, thus we will be evaluating the plants in September based on plant staging and development.
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Updated November 22, 2024:
Minnesota Soybean Research and Promotion Council
Research Progress Report
November 2024
Title: Addressing Management Challenges with Soybean Stem Diseases in Minnesota
Principal Investigator(s): Dean Malvick
Project Period Ending November 2024
Research Question/Objectives: This project focuses on the priority area of soybean pest management. It centers on research into managing against yield and quality limiting effects of stem diseases. Stem diseases are widespread and problematic across Minnesota. They damage plants and reduce yield and can go undetected and cause yield losses. Understanding more effective approaches to manage soybean stem diseases can result in yield increases. This proposed project targets management strategies for the diseases brown stem rot (BSR) and pod and stem blight (PSB). BSR is a common and important soybean disease in Minnesota. Crop rotations and resistant varieties can suppress BSR, however, neither method is a complete solution to managing the disease. Because BSR is a continuing problem for soybean production in Minnesota, more information is needed to understand risk factors and disease management options. Pod and stem blight is also a common and problematic disease in Minnesota soybean fields and likely causes more damage and yield loss than is recognized. Soybean varieties vary in resistance to PSB and crop rotation can be beneficial, but this disease and the best methods to manage it are poorly understood. In summary, this project is addressing short and long-term goals to manage the common and damaging soybean stem diseases brown stem rot (BSR) and pod and stem blight (PSB).
Project Updates for this period:
Objective one. Management of brown stem rot.
Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. In this project period, our work to develop and validate an improved and higher throughput method to evaluate soybean lines for resistance to BSR has provided additional results.: We completed a pilot greenhouse study. The results suggest that we can measure different amounts of the BSR pathogen in soybean stems shortly after inoculation in resistant and susceptible cultivars. Preliminary data suggests that differences in the pathogen quantity can be detected 3-4 weeks after inoculation and differentiate resistant and susceptible cultivars. Initial evaluation of another technique to quantify the pathogen in infected plants suggests that it is promising to use for low amounts of the pathogen, but more work is needed for us to determine how to best use this technique with our samples. The initial results overall suggest that this method, based on quantity of the pathogen in soybean stems, could potentially reduce cost, time, and challenges with evaluating resistance to BSR.
Goal B. Determine if seed treatments have value in managing BSR. The potential efficacy of seed treatment fungicides for managing BSR is unknown. Field studies were completed, and greenhouse and lab studies are ongoing to determine if common seed treatments are effective against BSR. Field studies were established in Waseca and Rosemount with different seed treatments in May 2024. The studies progressed well throughout the summer and were completed in October. Three seed treatments (ILEVO, Saltro, and Zeltera) were tested in the field for efficacy against BSR. Plants with the Saltro treatment had lower (but not significantly lower) incidence and severity of BSR stem symptoms compared to the untreated control. Studies in a greenhouse are underway and will be completed in December. The preliminary results from lab studies suggest that some fungicides may have suppressive effects on the BSR pathogen. More will be known when the lab and greenhouse work and analysis are finished early in the winter.
Goal C. Evaluate role of potential alternative hosts and crop rotation on risk and management of BSR. The BSR pathogen (Cadophora gregata) is reported to only infect soybean, adzuki bean, and mung bean, but this is poorly documented and understood. Thus, the host range of the BSR pathogens is unknown, which has implications for management of BSR with crop rotation. Twenty-seven crop and weed species have been evaluated in greenhouse experiments to determine if they can serve as hosts of the BSR pathogen. Initial results suggest that some plant, such as edible bean (Phaseolus vulgaris), may be hosts of C. gregata. Final testing and analysis of the plant samples will be completed in January to confirm if these and other plants are hosts of the BSR pathogen.
Objective two. Evaluate tactics to manage pod and stem blight of soybean. This project period has focused on field and greenhouse studies to study development and management of pod and stem blight of soybean. In field studies we used toothpick and wounding inoculation methods in a soybean field with irrigation to evaluate disease development with these methods and efficacy of foliar fungicides against pod and stem blight and stem canker. The inoculation methods did not work consistently, even with irrigation and/or adequate rain. Thus, it could not be determined if foliar fungicides are effective for managing pod and stem blight or stem canker. We also conducted greenhouse studies to determine if two seed treatments, ILEVO and Saltro, were have value in managing stem canker or pod and stem blight. There was no difference between the control and ILEVO treatments. Plants with the Saltro treatment had a slight reduction in stem canker symptoms. Currently, multiple soybean seed lines from the U of MN soybean breeding group are being tested in the greenhouse for resistance to stem canker and pod and stem blight.
Objective 3. Understand the distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota. We received samples from multiple locations early and late in the season to determine the cause of the plant stunting and death that was being seen in many fields. Dying seedlings from multiple locations received for diagnosis in the spring were found to have Rhizoctonia root and stem rot and Diaporthe sp. Soybean samples received at the end of the season had Diaporthe stem canker, pod and stem blight (Diaporthe), charcoal rot, Pythium root rot, SDS, and BSR. Many of the samples were found to be infected with multiple pathogens at the same time. Samples were evaluated by visible symptoms, isolations, and DNA analysis. Several of the samples that were received for confirmation of suspected SDS had both SDS and BSR or just BSR, and the results confirmed the increased incidence of SDS and BSR in western and NW Minnesota. This highlights the importance of correct diagnosis for these and other diseases... We also worked with a crop consultant in SE MN to understand the value of new soil plant pathogen testing technology being promoted by some companies, and the results overall were unclear.
Updated February 24, 2025:
Minnesota Soybean Research and Promotion Council
Research Progress Report
February 2025
Title: Addressing Management Challenges with Soybean Stem Diseases in Minnesota
Principal Investigator(s): Dean Malvick
Project Period Ending February 2025
Research Question/Objectives: This project focuses on the priority area of soybean pest management. It centers on research into managing against yield and quality limiting effects of soybean stem diseases. Stem diseases are widespread and problematic in soybean production fields across Minnesota. They damage plants and reduce yield and can go undetected yet cause yield losses. Understanding effective approaches to managing soybean stem diseases can result in yield increases.
This project targets management strategies for the diseases brown stem rot (BSR) and pod and stem blight (PSB). BSR is a common and important soybean disease in Minnesota. Crop rotations and resistant varieties can suppress BSR, but neither method can completely manage the disease. Because BSR is a continuing problem for soybean production in Minnesota, more information is needed to understand risk factors and disease management options. Pod and stem blight is also a common and problematic disease in Minnesota soybean fields. Soybean varieties vary in resistance to PSB and crop rotation can be beneficial, but this disease and the best methods to manage it are poorly understood. This project is addressing short and long-term goals to manage the common and damaging soybean stem diseases brown stem rot and pod and stem blight.
PROJECT UPDATES FOR THIS PERIOD:
Objective one. Management of brown stem rot.
Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. Studies are underway in a greenhouse to identify and characterize resistance to BSR in soybean lines from the U of MN soybean breeding project. That study is going well, and we expect the final results to be obtained in April. In this project period we also continued our work to develop and validate an improved and higher throughput method to evaluate soybean lines for resistance to BSR. Additional results from one completed study suggest that we can measure different amounts of the BSR pathogen in soybean stems of resistant and susceptible cultivars within 3 weeks after inoculation. Another greenhouse study to address this goal was planted and inoculated in the past month, and that project is expected to be completed in May. Our work with evaluation of another, newer technique to quantify the pathogen in infected plants suggests that it is promising to be used for detecting low amounts of the pathogen. Additional testing is in progress and will be done in the next project period to more fully evaluate this method. The initial results overall suggest that this approach, based on quantity of the pathogen in stems, can reduce time and challenges with evaluating resistance to BSR.
Goal B. Determine if seed treatments have value in managing BSR. The efficacy of soybean seed treatment fungicides for managing BSR has been, surprisingly, unknown. Lab studies have been completed to determine if common seed treatments are effective against the BSR pathogen (Cadophora gregata). The results suggest that several fungicides can suppress growth of the BSR pathogen at low doses. Final analysis of these results will be completed this spring.
Goal C. Evaluate the role of potential alternative hosts and crop rotation on risk and management of BSR. The BSR pathogen (Cadophora gregata) is known to only infect soybean, adzuki bean, and mung bean, but this is poorly documented and understood. Thus, the host range of the BSR pathogens is unknown, which has implications for management of BSR with crop rotation. Multiple crops and weed species were evaluated in greenhouse experiments to determine if they can serve as hosts of the BSR pathogen. Initial results suggest that some other crops are hosts of C. gregata, and final analysis will be completed this spring to confirm which of the tested plant species are hosts of the BSR pathogen.
Objective two. Evaluate tactics to manage pod and stem blight of soybean. This project period focused on greenhouse studies of development and management of pod and stem blight of soybean. The greenhouse studies suggest that some seed treatments may slightly reduce severity of stem canker. Multiple soybean seed lines from the U of MN soybean breeding group continue to be assessed in the greenhouse for resistance pod and stem blight, and those experiments will be completed in April 2025.
Objective three. Understand the distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota. This was a summer and fall project and thus has been completed. The summary of those results was included in the previous reports for this project.