This proposed project address the grower assessed priority area of Soybean Pest Management. It focuses on the need for research into managing against yield and quality limiting effects of root and stem rots.
Stem and root diseases are widespread and problematic in much of Minnesota. Sometimes they are very destructive and cause obvious plant death and yield loss. At other times, they are hidden from view and their significant effects on yield not obvious. If we understood when and where stem and root diseases occur more completely and managed them more effectively, yield in many fields could likely increase 5-10% in many areas and more in others.
Not only does this proposed project target management strategies for specific stem and root diseases e.g., SDS and brown stem rot (BSR) , it addresses a longer term goal of understanding the reasons for yield ‘drag’ in many fields and the role that disease plays. A key part of this is efforts to understand the distribution and importance of key diseases in Minnesota.
The changes in the occurrence and types of common soybean diseases (e.g. BSR, stem canker, pod an stem blight) and invasive or emerging diseases ( e.g. SDS, frogeye leaf spot) require that soybean growers and their advisors better understand these risks to plan for and react with appropriate management.
The management research focuses on key management strategies for SDS and BSR. SDS is a significant disease in Minnesota that is spreading to new areas. SDS was generally at low levels in 2021 due to dry conditions, but many fields are at risk of this disease when wet weather returns due to the long survival of the fungal pathogen. Seed treatments and partially resistant varieties are the main management options for SDS. A goal of this project is to develop robust results on the efficacy of varieties and seed treatments for managing SDS in different environments. This part of this project would build on the work conducted in 2021 and 2021. We obtained solid data in 20210, but the unusual dry and hot conditions in summer 2021 suppressed SDS development and reduced the value of the results in my research trials. Thus, this project would greatly benefit from one more year of data collected in more normal summer conditions. This will be the final year for this field study.
BSR is a common and significant recurring problem common across Minnesota. In summer 2021, BSR was common in Waseca, Rosemount, St Paul, and in multiple fields in SE MN. Partially resistant varieties and crop rotation are the main management options for SDS. This proposed project would address these two management options. First, by working with Aaron Lorenz to identify/characterize resistance/susceptibility to BSR in breeding lines and varieties adapted to MN. Second, to complete an ongoing project to determine the effects of short and long corn/soybean rotations on the risk of BSR. The results should clarify the risk of BSR in fields following different rotations and clarify how many years of rotation out of soybean are needed to reduce BSR.
In addition to the abovementioned work on management strategies for SDS and BSR, there is a need to understand the distribution of these and other root and stem key diseases. For example, although SDS has been spreading north and west, spread in the Red River Valley has not been confirmed. Thus, there is a need to determine where SDS has spread to and is occurring in the Red River valley. Other important diseases, e.g., BSR, pod and stem blight, stem canker, and charcoal rot all occur in MN. However, the distribution and frequency of these diseases in different areas is unknown. The last surveys of BSR, pod and stem blight, and stem canker were conducted in Minnesota over 10 years ago, and updated information is needed.

1. Determine the value of inputs and tactics for managing sudden death syndrome (SDS)
2. Evaluate tactics to manage brown stem rot (BSR) of soybean
3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

• This project will, determine the benefits of key seed treatments and resistant soybean varieties for management of SDS in multiple environments in Minnesota.
• Identify the level of BSR resistance in soybean breeding lines and varieties from the U of MN soybean-breeding program.
• Determine if new methods to evaluate soybean for resistance to BSR are more consistent, less expensive, and have higher throughput than current methods.
• Determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR
• Improve understanding of the distribution and risks of key soybean stem and root diseases to Minnesota soybean growers.
• Develop and extend updated information on the management, distribution, and risks of key soybean stem and root diseases for Minnesota soybean growers

Objective 1. Determine the efficacy of inputs and tactics for managing sudden death syndrome (SDS)

Background. SDS is among the most important soybean diseases in Minnesota. This disease is spreading in MN where it was previously uncommon. Thus, SDS is becoming a bigger problem in more areas, including more areas where high levels of resistance in locally adapted varieties is limited or absent. Because SDS is a continuing and spreading risk, we need to improve understanding of disease management options. Three seed treatments are widely marketed for management of SDS, but they can be an expensive input that may or may not pay-off with increased yields. There is a need to understand and compare management options for Minnesota. We have solid data from one year of conducting this study, and one more year will greatly enhance the reliability of the results.

Goal. The goal is to determine the benefits of three seed treatments (ILeVO®, Saltro®, and Heads-Up®) and resistant soybean varieties for management of SDS. Field trials will be conducted at two inoculated and irrigated field locations (Rosemount and Waseca, MN) with combinations of the seed treatments and soybean varieties with different levels of SDS resistance. Plots will be evaluated for the severity of SDS and for soybean yield.


Objective 2. Evaluate tactics to manage brown stem rot (BSR)

BSR is likely among the top five most important diseases in Minnesota. Crop rotations can suppress BSR and probably can reduce populations of the pathogen in the soil. Without knowing the pathogen population in the soil, however, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because BSR is a continuing threat to soybean production in Minnesota, we need more information to understand risk factors and disease management options.

Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. Advanced breeding lines from the U of MN soybean-breeding program, as well as selected commercial soybean varieties, will be evaluated for resistance to BSR. This work will be conducted in cooperation with Dr. Aaron Lorenz. This research will primarily be conducted in a greenhouse under controlled conditions, although limited work will also be conducted in field studies. . Plants in the greenhouse at the VC/V1 growth stage will be inoculated in replicated studies with two types (A and B) of the BSR pathogen. BSR severity will be measured after the R6 growth stage. In addition, because BSR resistance is difficult and time consuming to evaluate, we also aim to compare different resistance testing methods with the goal of developing a method that is simpler, consistent, and has higher throughput for breeding and research needs.

Goal B. This goal is to determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR. Soil samples from long-term crop rotation plots in Waseca will be tested to determine the effect of rotation on populations of the BSR pathogen in the soil. Complementary research will be conducted in replicated studies under controlled environmental conditions in a greenhouse. Quantitative PCR will be used to estimate pathogen populations (inoculum potential) in soil and infection of plants.


Objective 3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

Increasing and even maintaining soybean yields in the presence of new and evolving pathogens and diseases requires continued improvements in soybean varieties, fungicides, and crop management practices. New pathogens and new disease management practices require more information to manage and use them most effectively. For example, the seed treatments for SDS are expensive and may only be beneficial where SDS occurs, and thus knowing when and where SDS is problematic can improve our abilities to use these products most effectively. Thus, there is a need for increased disease/pathogen survey activity to detect and understand how risks from key soybean diseases are changing and where and when they occur. Stem pathogen surveys have not been done in over 10 years, and new survey efforts and needed to provide a current ‘picture’ of prevalence and distribution of types A and B of BSR, pod and stem blight, stem canker, and charcoal rot.
We plan to survey for soybean stem and root diseases to better understand their current distribution and risk to Minnesota soybean growers. The results will guide disease management priorities. Surveys will be conducted in August and September to determine the prevalence of key diseases in multiple regions across the state. Samples will be collected from problematic and ‘healthy’ looking commercial fields and at the Research and Outreach Centers. Then plants will be diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The new molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases.

Update:
Progress and results through July 31:

For each part of this project, a summary of activity and progress is summarized below for this reporting period. If you would like additional information about this project and the results, please let me know. Thank you.

Objective 1. Field studies were established in May 2022 at two field locations in Minnesota (Rosemount and Waseca, MN) to determine the effects of the three seed treatments on development of SDS and on yield. In total, 5 treatments (including controls) were included on each of two different soybean varieties that have different levels of SDS resistance. The plots were all inoculated with the SDS pathogen (Fusarium virguliforme) at the time of planting, and plots have been irrigated throughout the summer to enhance infection and SDS development. The studies have been established exactly as planned and were growing well and looking good through the end of July. Looking ahead, in August we will see how much SDS develops and disease ratings will be obtained from all plots at both locations on at least two different dates and growth stages. Finally, seed yield will be determined in late September or October.

Objective 2. Progress and results to date:
The work for Goal A will commence this fall and winter in the greenhouses on campus in St Paul. For Goal B, soil samples will be collected in the fall and the majority of this work will also be conducted in my laboratory in the fall and winter.

Objective 3. Progress and results to date:
Soybean stem and root diseases (especially those focused on for this project), primarily become problematic in the late summer and early fall. Thus our survey efforts will commence in August and September to address this objective.

Update:
Quarterly Progress Report for 2023-2023 Minnesota Soybean Research and Promotion Council Production Action Team


Project Title: Soybean Stem and Root Diseases: Filling the Gaps for Management

• Principle Investigator: Dean Malvick
• Department/Organization: Department of Plant Pathology, University of Minnesota, St. Paul, MN

• Dates of Reporting: August 1 – November 30 , 2022

Activity and progress for each part of this project is summarized below for this reporting period. Please let me know if you would like additional information. Thank you.

Objectives for this project:
1. Determine the efficacy of inputs and tactics to manage sudden death syndrome (SDS)
2. Evaluate tactics to manage brown stem rot (BSR) of soybean
3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

Progress Report by Objective

1. Determine efficacy of inputs and tactics to manage sudden death syndrome (SDS)

Background. SDS is among the most important soybean diseases in Minnesota. This disease is spreading in MN where it was previously uncommon. Thus, SDS is becoming a bigger problem in more areas, including more areas where high levels of resistance in locally adapted varieties is limited or absent. Because SDS is a continuing and spreading risk, we need to improve understanding of disease management options. Three seed treatments are widely marketed for management of SDS, but they can be an expensive input that may or may not pay-off with increased yields. There is a need to understand and compare management options for Minnesota.

Goal. The goal is to determine the benefits of three seed treatments (ILeVO®, Saltro®, and Heads-Up®) and resistant soybean varieties for management of SDS. Field trials will be conducted at two inoculated and irrigated field locations (Rosemount and Waseca, MN) with combinations of the seed treatments and soybean varieties with different levels of SDS resistance. Plots will be evaluated for the severity of SDS and for soybean yield.

Progress and results to date:
Field studies were conducted at the two field locations in 2022 to determine the effects of the three seed treatments (noted above) on development of SDS and on soybean yield. Soybeans were planted in May at Rosemount and Waseca, MN. In total, five treatments (including controls) were included on each of two soybean varieties that have different levels of SDS resistance. The plots were all inoculated with the SDS pathogen (Fusarium virguliforme) at the time of planting and were irrigated throughout the summer to enhance infection and SDS development. Thus, the studies were established and conducted as planned, and the plants grew well and looked good throughout the season. Severity and incidence of SDS were evaluated in all plots at both locations on two different dates and growth stages. Seed yield was measured with a plot combine from all plots in early October.

In spite of inoculating and irrigating the plots, only low levels of SDS developed at each location. There were slightly higher levels of SDS at Rosemount than Waseca. The seed treatments reduced SDS development, but they had very little effect on yield at either location. The SDS levels were likely too low and the disease developed too late to have a strong impact on yield in these studies. Results for SDS Dx (a combination of disease incidence and severity) and soybean yield are shown below for the field studies at Rosemount and Waseca.




Objective 2. Evaluate tactics to manage brown stem rot (BSR)

BSR is likely among the top five most important diseases in Minnesota, and was very common in some fields in central and southern MN in 2022. Crop rotations can suppress BSR and likely can reduce populations of the pathogen in the soil. Without knowing the pathogen population in the soil, however, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because BSR is a continuing threat to soybean production in Minnesota, we need more information to understand risk factors and disease management options.

Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. Advanced breeding lines from the U of MN soybean-breeding program and selected commercial soybean varieties will be evaluated for resistance to BSR. This will be conducted in cooperation with Dr. Aaron Lorenz and his soybean breeding program. The work will be done primarily in a greenhouse under controlled conditions. Plants will be inoculated at the VC/V1 growth stage in replicated studies with two types (A and B) of the BSR pathogen (Cadophora gregata). BSR severity will be measured at the R6 growth stage. In addition, because BSR resistance is difficult and time-consuming to evaluate, we also aim to compare different resistance testing methods with the goal of developing a method that is consistent, faster, and has higher throughput for breeding and research needs.

Goal B. This goal is to determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR. Soil samples from long-term crop rotation plots in Waseca will be tested to determine the effect of rotation on populations of the BSR pathogen in the soil. Complementary research will be conducted in replicated studies under controlled environmental conditions in a greenhouse. Quantitative PCR will be used to estimate pathogen populations (inoculum potential) in soil and plants.

Progress and results to date:
For Goal A, the primary work on evaluating soybean varieties for resistance to both genotypes of the BSR pathogen will be conducted this winter in the greenhouses on campus in St Paul. We plan to start the studies in mid-December and complete them by March. The work to compare different methods to evaluate soybean varieties for resistance to BSR has been progressing in the growth chamber and lab. Initial results suggest that resistance to BSR can be measured sooner when evaluation is done based on pathogen colonization (pathogen DNA quantity) in the stems than with symptom development, which could greatly increase throughput for BSR resistance screening. Additional experiments and data analysis are underway to finalize these studies.
For Goal B, additional soil samples will be analyzed this winter to determine if crop rotation can have a clear effect on reducing the pathogen population in the soil.


Objective 3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

Increasing and even maintaining soybean yields in the presence of new and evolving pathogens and diseases requires continued improvements in soybean varieties, fungicides, and crop management practices. New pathogens and new disease management practices require more information to manage and use them most effectively. For example, the seed treatments for SDS are expensive and may only be beneficial where SDS occurs, and thus knowing when and where SDS is problematic can improve our abilities to use these products most effectively and economically. Thus, there is a need for increased disease/pathogen survey activity to detect and understand how risks from key soybean diseases are changing and where and when they occur. Stem pathogen surveys have not been done in over 10 years, and new survey efforts and needed to provide a current ‘picture’ of prevalence and distribution of types A and B of BSR, pod and stem blight, stem canker, and charcoal rot.
Surveys for soybean stem and root diseases will be done to better understand their current distribution and risk to Minnesota soybean growers. The results will guide disease management priorities. Surveys will be conducted in August and September to determine the prevalence of key diseases in multiple regions across the state. Samples will be collected from problematic and ‘healthy’ looking commercial fields and at the Research and Outreach Centers. Then plants will be diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The new molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases.
Progress and results to date:
Soybean stem and root diseases (especially those focused on for this project), primarily become problematic in the late summer and early fall. Our survey efforts focused on plants collected from eight soybean fields in central and southern Minnesota in September to address this objective. The number of samples was relatively low this year due to low participation in sampling by cooperators. However, this is still enabling us to improve and perfect our pathogen detection methods and gain some interesting results based on preliminary data. Sample analysis and results confirmation is underway and will be completed in January.


Information Dissemination of data/information from this research during this reporting period.
• A field day was conducted in early September in Rosemount, MN to demonstrate and discuss results from this project.
• I brought a group of plant pathology graduate students to view the soybean SDS field study in Rosemount, MN in August to demonstrate and discuss results from this project, and to improve their knowledge of soybeans and soybean diseases.
• Results were presented and discussed with a large group (>100) of farmers) at an annual crops meeting in Trimont, MN in November.
• Results from the SDS research were presented to a group of regional and national researchers and agronomists with Bayer Crop Science as well as a group of Extension Educators in November in Shakopee, MN.

Update:
Quarterly Progress Report for 2023-2023 Minnesota Soybean Research and Promotion Council Production Action Team

Project Title: Soybean Stem and Root Diseases: Filling the Gaps for Management

• Principle Investigator: Dean Malvick
• Department/Organization: Department of Plant Pathology, University of Minnesota, St. Paul, MN.
• Dates of Reporting: Dec 1, 2022, to Feb 27, 2023

The activity and progress for each part of this project is summarized for this reporting period. Please let me know if you would like additional information. Thank you.

Objectives for this project:
1. Determine the efficacy of inputs and tactics to manage sudden death syndrome (SDS)
2. Evaluate tactics to manage brown stem rot (BSR) of soybean
3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

Progress Report by Objective

1. Determine efficacy of inputs and tactics to manage sudden death syndrome (SDS)

Background. SDS is among the most important soybean diseases in Minnesota. This disease is common across southern MN, and is spreading into other areas where it was uncommon. Thus, SDS is becoming a more widespread problem, including more areas where high levels of resistance in locally adapted varieties is limited. Because SDS is an increasing risk, there has been a continuing need to improve understanding of disease management options. Three seed treatments are widely marketed for management of SDS, but they can be expensive inputs that may or may not pay-off with increased yields. There is a need to understand management options for Minnesota.

Goal. The goal is to determine the benefits of three seed treatments (ILeVO®, Saltro®, and Heads-Up®) and resistant soybean varieties for management of SDS. Field trials were conducted at two inoculated and irrigated field locations (Rosemount and Waseca, MN) with combinations of the seed treatments and soybean varieties with different levels of SDS resistance. Plots were evaluated for the severity of SDS and for soybean yield.
Progress and Results: Field studies were conducted and completed at the two field locations in 2022 to determine the effects of the three seed treatments (noted above) on development of SDS and soybean yield. Soybeans were planted in May at both field trial locations. In total, five treatments (including controls) were included on each of two soybean varieties that have different levels of SDS resistance. The plots were inoculated with the SDS pathogen (Fusarium virguliforme) at the time of planting and were irrigated throughout the summer to enhance infection and SDS development. Thus, the studies were established and conducted as planned, and the plants grew well throughout the season. Severity and incidence of SDS were assessed at both locations on two different dates and growth stages in August, and seed yields in all treatments were measured with a plot combine in October.
Low levels of SDS developed in both trials, even though we inoculated and irrigated the plots. Severity and incidence of disease were lower than in previous years. Slightly higher levels of SDS developed at Rosemount than Waseca. The seed treatments reduced SDS development, but they had minimal effects on yield at either location. This was likely due to the SDS levels likely being too low and the disease developing too late to have a strong impact on yield in these studies.


Objective 2. Evaluate tactics to manage brown stem rot (BSR)

BSR is likely among the top five most important diseases in Minnesota, and was very common in some fields in central and southern MN again in 2022. Crop rotations can suppress BSR and likely can reduce populations of the pathogen in the soil. Without knowing the pathogen population in the soil, however, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because BSR is a continuing threat to soybean production in Minnesota, we need more information to understand risk factors and disease management options.

Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. Advanced breeding lines from the U of MN soybean-breeding program and selected commercial soybean varieties were evaluated for resistance to BSR. This was done in cooperation with Dr. Aaron Lorenz and his soybean breeding program. The work was done in a greenhouse under controlled conditions. Plants were inoculated at the VC/V1 growth stage in replicated studies with types A and B of the BSR pathogen (Cadophora gregata). BSR severity was then measured about 7 weeks later at the R6 growth stage.
Progress and results to date: The primary work on evaluating soybean varieties for resistance to both genotypes of the BSR pathogen was completed in February in the greenhouses on campus in St Paul. We started the studies in mid-December and completed them in late February. The soybean entries evaluated had a range of levels of susceptibility to both types (A and B) of BSR, ranging from moderate levels of resistance to high levels of susceptibility. These data will be useful for continued breeding efforts with these lines. For the other part of this project, the work to compare different methods to evaluate soybean varieties for resistance to BSR has progressed. The results suggest that resistance to BSR can be measured sooner when evaluation is done based on pathogen colonization (pathogen DNA quantity) in the stems than with symptom development. This method could greatly increase throughput for BSR resistance screening. Further analysis is underway to conclude these studies.

Goal B. This goal is to determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR. Soil samples from long-term crop rotation plots in Waseca have tested with quantitative PCR to determine the effect of rotation on populations of the BSR pathogen in the soil.
Progress and results to date: Additional analyses of the soil samples are underway this winter to determine if crop rotation can have a clear effect on reducing the pathogen population in the soil. Initial results suggest the suppressive role that rotation have on soil populations, and addition analysis will be conducted this winter and spring to develop conclusions.


Objective 3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota

Increasing and maintaining soybean yields in the presence of new and evolving pathogens and diseases requires continued improvements in soybean varieties, fungicides, and crop management practices. New pathogens and new disease management practices require more information to manage and use them most effectively. For example, the seed treatments for SDS are expensive and may only be beneficial where SDS occurs, and thus knowing when and where SDS is problematic can improve our abilities to use these products most effectively and economically. Thus, there is a need for increased disease/pathogen survey activity to detect and understand how risks from key soybean diseases are changing and where and when they occur. Stem pathogen surveys have not been done in over 10 years, and new survey efforts are needed to provide a current ‘picture’ of prevalence and distribution of types A and B of BSR, pod and stem blight, stem canker, and charcoal rot.
A limited survey for soybean stem and root diseases was done in August and September to better understand their current distribution and risk to Minnesota soybean growers. The results will guide disease management priorities and enhance further survey efforts. Samples were collected from eight problematic and ‘healthy’ looking commercial fields and at the Research and Outreach Centers. The number of samples was relatively low this year in part due to low participation by cooperators. However, this is enabling us to improve and perfect our pathogen detection methods and gain interesting results based on preliminary data. Then plants were diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases. All of the pathogens/diseases that we tested for were detected at high incidence, suggesting a widespread distribution and common infection by these pathogens.

Information Dissemination of data/information from this research during this reporting period.
• Results were presented/discussed at Research Update Meetings in Waseca, Lamberton, Wilmar, and Morris, MN in January 2023.
• Results from the SDS research were presented at the Best of the Best conferences in soybean and wheat research in Grand Forks and Moorhead in February
• Results were presented and discussed at a meeting of Independent Crop Consultants in Bloomington in February.
• Results were shared and discussed at AgExpo in Mankato in January
• Results were shared and discussed at Winter Crops Day in Waseca in January

Update:
Progress Report by Objective

1. Determine efficacy of inputs and tactics to manage sudden death syndrome (SDS)

Background. Sudden death syndrome (SDS) is among the most important soybean diseases in Minnesota and upper Midwest. This disease is common across southern Minnesota and is also spreading into areas where it was previously uncommon. Thus, SDS is becoming a more widespread problem, including in more areas where high levels of resistance in locally adapted varieties is limited. Because SDS is an increasing risk, there has been a continuing need to improve understanding of disease management options. Soybean varieties are available with various levels of resistance to SDS and seed treatments are now available for management of SDS. Three seed treatments are widely marketed for management of SDS, but they can be expensive inputs that may or may not pay-off with increased yields. Thus, there is a need to determine the efficacy and relative benefits of these different management options for SDS in Minnesota.

Goal. The goal of this project was to determine the value of three seed treatments (ILeVO®, Saltro®, and Heads-Up®) and resistant soybean varieties for managing SDS.

Experimental Approach. Replicated field studies were conducted at two locations (Rosemount and Waseca, MN) in 2022. The treatments included all combinations of three seed treatments and two soybean varieties with different levels of SDS resistance. In total, five treatments (including controls and base seed treatment alone) were included on each of the two soybean varieties. Seed was treated on the St Paul campus using a rotating drum tabletop lab seed treater. The plots (10 ft wide by 25 ft long) were inoculated with the SDS pathogen (Fusarium virguliforme) and irrigated to enhance development of SDS. All plots were evaluated for the severity and incidence of SDS at two growth stages, and Dx score for SDS was calculated based on the incidence and severity of SDS. Soybean yield was measured with a plot combine at maturity in October.

Progress and results: The field studies were conducted and completed at the two field locations in 2022 to determine the effects of the three seed treatments (noted above) combined with two soybean varieties on development of SDS and soybean yield. Soybeans were planted in May at Rosemount and Waseca, MN. The studies were conducted as planned, and the plants grew well throughout the season.

The summer was exceptionally dry and warm at both field locations in 2022. Low levels of SDS developed at each trial location despite the inoculation and irrigation that was applied to the plots. Slightly higher levels of SDS developed at Rosemount than Waseca, but the Dx score for SDS at both locations was low compared to previous years. In Rosemount, SDS levels were low with an average foliar incidence of 2% in the untreated susceptible plots. In Waseca, SDS levels were more moderate with an average foliar incidence of 15% in the untreated susceptible plots. The seed treatments reduced SDS development but had minimal effects on yield at either location in 2022. This was likely due to the low incidence and the slow and late development of SDS. The results for the different seed treatments and soybean varieties on SDS Dx score and soybean yield are shown below for the studies at Rosemount and Waseca.



Results from field studies conducted in Rosemount and Waseca, MN in 2022 to determine the value of five selected seed treatments and two soybean varieties for managing SDS. Note that red bars represent yield and blue bars represent SDS incidence and severity (Dx score).

Objective 2. Evaluate tactics to manage brown stem rot (BSR)

Brown stem rot (BSR) is likely among the top five most important diseases in Minnesota and was common again in fields in central and southern MN in 2022. Crop rotations can suppress BSR and can reduce populations of the pathogen in the soil. Without knowing the pathogen population in the soil, however, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because BSR is a continuing threat to soybean production in Minnesota, more information is needed to understand risk factors and disease management options.

Goal A. Evaluate soybean breeding lines and varieties for resistance to BSR. Advanced breeding lines from the U of MN soybean-breeding program and selected commercial soybean varieties were evaluated for resistance to BSR. This was done in cooperation with Dr. Aaron Lorenz and his soybean breeding program. The work was conducted in a greenhouse under controlled conditions. Plants were inoculated at the VC/V1 growth stage in replicated studies with two types (A and B) of the BSR pathogen (Cadophora gregata). BSR stem and leaf severity was measured at the R6 growth stage. In addition, because BSR resistance is difficult and time-consuming to evaluate, we also worked to evaluate different resistance testing methods with the goal of developing a method that is consistent and has higher throughput for breeding and research needs.

Goal B. This goal is to determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR. Soil samples from long-term crop rotation plots in Waseca were collected and tested to determine the effect of rotation on populations of the BSR pathogen in the soil. A quantitative PCR (qPCR) method was used to estimate pathogen populations (inoculum potential) in soil.

Progress and results:
For Goal A, the primary work on evaluating soybean varieties and breeding lines for resistance to both genotypes of the BSR pathogen was conducted in greenhouses on campus in St Paul. The studies were initiated in December and completed in February.
The data reveal various levels of susceptibility/resistance among the soybean entries evaluated to types A and B of the BSR pathogen. Studies were also conducted to determine if we can detect and measure BSR resistance sooner using a new method. The initial results from this work suggest that resistance to BSR can be measured sooner when evaluation is done based on pathogen colonization (pathogen DNA quantity) in the stems than with symptom development, which could increase throughput for BSR resistance screening. Additional studies are needed to determine the feasibility of this new method.

For Goal B. Multiple soil samples from fields with different crop rotation histories have been tested with a PCR assay to determine the quantity of the BSR pathogen in the soil. Initial results suggest a relationship between soil populations of the BSR pathogen and crop rotation history of a field, but the results are not as clear as we would like and more analysis of the data is needed and will be conducted.

Objective 3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota.

Increasing and even maintaining soybean yields in the presence of new and evolving pathogens and diseases requires continued improvement in soybean varieties, fungicides, and crop management practices. New pathogens and new disease management practices require more information to manage and use them most effectively. For example, the seed treatments for SDS are expensive and may only be beneficial where SDS occurs, and thus knowing when and where SDS has spread can improve our abilities to use these products most effectively and economically. Thus, there is a need for increased disease/pathogen survey activity to detect and understand how risks from key soybean diseases are changing and where they occur. Stem pathogen surveys have not been done in over 10 years, and new survey efforts and needed to provide a more current ‘picture’ of prevalence and distribution of types A and B of BSR, pod and stem blight, stem canker, and charcoal rot.
Surveys for soybean stem and root diseases are needed to better understand their current distribution and risk to Minnesota soybean growers. The results will guide disease management priorities. The survey was conducted in August and September to determine the prevalence of key diseases in selected areas in central and southern MN. Samples were collected from problematic and ‘healthy’ looking commercial fields and research sites. Then plants will be diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The new molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases.
Progress and results: Soybean stem and root diseases become problematic in multiple fields and areas in the late summer and early fall. A limited survey for soybean stem and root diseases was done in August and September to evaluate and develop methods and to better understand their current distribution and risk to Minnesota soybean growers. Samples were collected from eight problematic and ‘healthy’ looking commercial fields and at Research and Outreach Centers. The number of samples was low this year in part due to low participation by cooperators and drought conditions. However, this is enabling us to evaluate and perfect our pathogen detection methods and gain interesting results based on preliminary data. Then plants were diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases. The pathogens/diseases that we tested for (BSR types A and B, pod and stem blight, stem canker, and charcoal rot) were detected in the samples at frequencies of 25-100%, suggesting widespread distribution and common infection by these pathogens in the region sampled.



Information Dissemination of data/information from this research over this project period.
• A field day was conducted in early September in Rosemount, MN to demonstrate and discuss results from this project.
• I brought a group of plant pathology graduate students to view the soybean SDS field study in Rosemount, MN in August to demonstrate and discuss results from this project, and to improve their knowledge of soybeans and soybean diseases.
• Results were presented and discussed with a large group (>100 farmers) at an annual crops meeting in Trimont, MN in November.
• Results from the SDS research were presented to a group of regional and national researchers and agronomists with Bayer Crop Science as well as a group of Extension Educators in November in Shakopee, MN.
• Results were presented and discussed at Research Update Meetings at Waseca, Lamberton, Wilmar, and Morris in January 2023.
• Results from SDS research were presented at the Best of the Best conferences in soybean and wheat research in Grand Forks, ND and Moorhead, MN in February
• Results were presented and discussed at a meeting of Independent Crop Consultants in Bloomington, MN in February.
• Results were shared and discussed at AgExpo in Mankato in January
• Results were shared and discussed at Winter Crops Day in Waseca in January

View uploaded report

Final Report for 2023-2023 Minnesota Soybean Research and Promotion Council Production Action Team

Project Title: Soybean Stem and Root Diseases: Filling the Gaps for Management
• Principle Investigator: Dean Malvick
• Department/Organization: Department of Plant Pathology, University of Minnesota, St. Paul, MN.
• Final Report for period May 1, 2022, to April 30, 2023

Project One. Determine efficacy of inputs and tactics to manage sudden death syndrome (SDS). Sudden death syndrome (SDS) is among the most important soybean diseases in Minnesota and upper Midwest. This disease is common across southern Minnesota and is also spreading into areas where it was previously uncommon. Thus, SDS is becoming a more widespread problem, including in more areas where high levels of resistance in locally adapted varieties is limited. Because SDS is an increasing risk, there has been a continuing need to improve understanding of disease management options. Soybean varieties are available with various levels of resistance to SDS and seed treatments are now available for management of SDS. Several seed treatments are widely marketed for management of SDS, but they can be expensive inputs that may or may not pay-off with increased yields. Thus, there is a need to determine the efficacy and relative benefits of these different management options for SDS in Minnesota. The primary goal of this project was to determine the value of three seed treatments (ILeVO®, Saltro®, and Heads-Up®) and resistant soybean varieties for managing SDS.
Replicated field studies were conducted at two locations (Rosemount and Waseca, MN) in 2022. The treatments included all combinations of three seed treatments and two soybean varieties with different levels of SDS resistance. In total, five treatments (including controls and base seed treatment alone) were included on each of the two soybean varieties. Seed was treated on the St Paul campus using a rotating drum tabletop lab seed treater. The plots (10 ft wide by 25 ft long) were inoculated with the SDS pathogen (Fusarium virguliforme) and irrigated to enhance development of SDS. All plots were evaluated for the severity and incidence of SDS at two growth stages, and Dx score for SDS was calculated based on the incidence and severity of SDS. Soybean yield was measured with a plot combine at maturity in October.
The summer was exceptionally dry and warm at both field locations in 2022. Low levels of SDS developed at each trial location despite the inoculation and irrigation that was applied to the plots. Slightly higher levels of SDS developed at Rosemount than Waseca, but the Dx score for SDS at both locations was low compared to previous years. In Rosemount, SDS levels were low with an average foliar incidence of 2% in the untreated susceptible plots. In Waseca, SDS levels were more moderate with an average foliar incidence of 15% in the untreated susceptible plots. The seed treatments reduced SDS development but had minimal effects on yield at either location in 2022. This was likely due to the low incidence and the slow and late development of SDS. The results for the different seed treatments and soybean varieties on SDS Dx score and soybean yield are shown below for the studies at Rosemount and Waseca.

Project 2. Evaluate tactics to manage brown stem rot (BSR). Brown stem rot (BSR) is likely among the top five most important diseases in Minnesota and was common again in fields in central and southern MN in 2022. Crop rotations can suppress BSR and can reduce populations of the pathogen in the soil. Without knowing the pathogen population in the soil, however, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because BSR is a continuing threat to soybean production in Minnesota, more information is needed to understand risk factors and disease management options.
The first goal of this project was to evaluate soybean breeding lines and varieties for resistance to BSR. Advanced breeding lines from the U of MN soybean-breeding program and selected commercial soybean varieties were evaluated for resistance to BSR. This was done in cooperation with Dr. Aaron Lorenz and his soybean breeding program. The work was conducted in a greenhouse under controlled conditions. Plants were inoculated at the VC/V1 growth stage in replicated studies with two types (A and B) of the BSR pathogen (Cadophora gregata). BSR stem and leaf severity was measured at the R6 growth stage. In addition, because BSR resistance is difficult and time-consuming to evaluate, we also worked to evaluate different resistance testing methods with the goal of developing a method that is consistent and has higher throughput for breeding and research needs.
The second goal of this project is goal is to determine the effects of crop rotation and BSR pathogen populations in soil on risk and management of BSR. Soil samples from long-term crop rotation plots in Waseca were collected and tested to determine the effect of rotation on populations of the BSR pathogen in the soil. A quantitative PCR (qPCR) method was used to estimate pathogen populations (inoculum potential) in soil.
For the first goal, the work to evaluate soybean varieties and breeding lines for resistance to both genotypes of the BSR pathogen was conducted in greenhouses on campus in St Paul. The studies were initiated in December and completed in February.
The data reveal various levels of susceptibility/resistance among the soybean entries evaluated to types A and B of the BSR pathogen. Studies were also conducted to determine if we can detect and measure BSR resistance sooner using a new method. The initial results from this work suggest that resistance to BSR can be measured sooner when evaluation is done based on pathogen colonization (pathogen DNA quantity) in the stems than with symptom development, which could increase throughput for BSR resistance screening. Additional studies are needed to determine the feasibility of this new method.
For the second goal, multiple soil samples from fields with different crop rotation histories have been tested with a PCR assay to determine the quantity of the BSR pathogen in the soil. Initial results suggest a relationship between soil populations of the BSR pathogen and crop rotation history of a field, but the results are not as clear as we would like and more analysis of the data is needed and will be conducted.

Project 3. Increase survey efforts to determine distribution and prevalence of important soybean stem and root diseases/pathogens in Minnesota. Increasing and even maintaining soybean yields in the presence of new and evolving pathogens and diseases requires continued improvement in soybean varieties, fungicides, and crop management practices. New pathogens and new disease management practices require more information to manage and use them most effectively. For example, the seed treatments for SDS are expensive and may only be beneficial where SDS occurs, and thus knowing when and where SDS has spread can improve our abilities to use these products most effectively and economically. Thus, there is a need for increased disease/pathogen survey activity to detect and understand how risks from key soybean diseases are changing and where they occur. Stem pathogen surveys have not been done in over 10 years, and new survey efforts and needed to provide a more current ‘picture’ of prevalence and distribution of types A and B of BSR, pod and stem blight, stem canker, and charcoal rot.
Surveys for soybean stem and root diseases are needed to better understand their current distribution and risk to Minnesota soybean growers. The results will guide disease management priorities. The survey was conducted in August and September to determine the prevalence of key diseases in selected areas in central and southern MN. Samples were collected from problematic and ‘healthy’ looking commercial fields and research sites. Then plants will be diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The new molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases.
Soybean stem and root diseases become problematic in multiple fields and areas in the late summer and early fall. A limited survey for soybean stem and root diseases was done in August and September to evaluate and develop methods and to better understand their current distribution and risk to Minnesota soybean growers. Samples were collected from eight problematic and ‘healthy’ looking commercial fields and at Research and Outreach Centers. The number of samples was low this year in part due to low participation by cooperators and drought conditions. However, this is enabling us to evaluate and perfect our pathogen detection methods and gain interesting results based on preliminary data. Then plants were diagnosed in a laboratory to identify symptoms and the presence of key pathogens using pathogen isolation methods and specific DNA diagnostic tests. The molecular tools based on DNA analysis improved our abilities to test samples in the laboratory for the presence of these diseases. The pathogens/diseases that we tested for (BSR types A and B, pod and stem blight, stem canker, and charcoal rot) were detected in the samples at frequencies of 25-100%, suggesting widespread distribution and common infection by these pathogens in the region sampled.

Information and results from this project were presented at meetings and conferences around Minnesota over this project period. This included a field day in September in Rosemount, MN, a large grower meeting in southern MN in November, a meeting with regional and national researchers and agronomists in November, Research Update Meetings at Lamberton, Wilmar, and Morris in January; the Best of the Best conferences in soybean and wheat research in Grand Forks, ND and Moorhead, MN in February; a meeting with crop consultants in Bloomington, MN in February, the AgExpo in Mankato in January, and Winter Crops Day in Waseca in January.

This project, as outlined with each of the deliverables, will address the need for improved understanding and management of key soybean diseases that reduce soybean yields across Minnesota. Enhanced understanding of where stem and root diseases occur and managing them more effectively should result in increased soybean yields in many fields. Thus, this research will produce information to improve disease management and reduce risk and yield-loss for soybean. Results will be transferred through newsletters, production meetings and field days, scientific meetings, and news outlets. The ultimate benefit to soybean growers will be increased yields and reduced risk of lost yields due to disease.