This proposal addresses the 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 and foliar diseases. This is for phase 2 for a 2-year project initiated in 2020. Thus, the project goals are similar to those addressed in 2020. There is a need to obtain replicated results from field studies repeated over 2 years in different environments to obtain clear and solid results. This project focuses on stem and root diseases of soybean, primarily sudden death syndrome (SDS), brown stem rot (BSR), and frogeye leaf spot. These diseases limit yields in fields across Minnesota and are generally difficult to manage. SDS is a significant disease in Minnesota where it is spreading and causing more problems in areas where it has not before. Frogeye leaf spot has long been a significant disease across the southern half of the U.S., and has been increasing in Minnesota and nearby states. BSR is a common across Minnesota, and is a significant recurring problem that requires continued management to increase yields. The goal of this project is to evaluate the value of seed treatments and resistant varieties for these diseases. 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.

1. Evaluate inputs and tactics to manage SDS and BSR of soybean
2. Determine distribution of Frogeye Leaf Spot in Minnesota and evaluate fungicide efficacy against Minnesota isolates of the causal pathogen
3. Conduct extension education and diagnostic activities that address important and unusual soybean disease problems in Minnesota.

Plan of Work by Objective:
1. Evaluate inputs and tactics to manage SDS and BSR of soybean.
Background. SDS and BSR are among the top 10 soybean diseases in the NC Region based on USB-sponsored yield loss estimates, and are likely among the top five most important diseases in Minnesota. SDS is spreading west and north in Minnesota (and in North Dakota) into areas where it was previously uncommon, probably in response to wetter summers and spread of the pathogen over time. Thus, SDS is becoming a bigger problem in more areas, especially in more areas where high levels of resistance in locally adapted varieties is limited or absent. Several seed treatments are sold for management of SDS, however, they are an expensive input cost that may or may not pay-off with increased yields. There is a need to understand and compare new and ‘old’ management options for Minnesota. Results from the studies my research team conducted in 2019 suggest that some seed treatments can be effective for managing SDS. Additional field studies are needed to validate these results and provide better data to assess the situations where they are most likely to pay off.
BSR occurs in all soybean production areas of MN including those areas where SDS is spreading. BSR can be confused with SDS based on leaf symptoms. Soil populations of the SDS and BSR pathogens influence disease risk and may influence efficacy of disease resistance. Resistance and crop rotations can be used to manage BSR. However, resistance in not known in available public varieties and Minnesota breeding lines and needs to be evaluated. In addition, without knowing the BSR pathogen population in the soil, it is only a guess as to how effective the rotations are and when BSR-susceptible varieties can be planted with minimal risk. Because SDS and BSR are threats to soybean production in Minnesota, it is important understand risk factors and disease management options for both

Goals and Approach/Methods:
A. The primary goal is to determine the benefits of four seed treatments (ILeVO®, Saltro®, base treatment, and Heads-Up®) and resistant soybean varieties for management of SDS in different field environments. Trials will be conducted at inoculated and irrigated fields in Rosemount and Waseca, MN with combinations of the seed treatments and soybean varieties with two levels of SDS resistance. Data for SDS severity and yield will be collected.
B. Evaluate available public varieties and soybean breeding lines for resistance to BSR . Available public varieties and advanced breeding lines from the U of MN soybean-breeding program, as well as selected common commercial soybean varieties, will be evaluated for resistance to BSR. This work will be conducted in cooperation with Dr. Aaron Lorenz. This research will be conducted in a greenhouse under controlled conditions, and different methods for evaluating resistance will be tested. Plants at the VC/V1 growth stage will be inoculated in replicated studies with two types (A and B) of the BSR pathogen. BSR severity and plant growth will be measured after the R6 growth stage.

2. Determine distribution of Frogeye Leaf Spot in Minnesota and evaluate fungicide activity against Minnesota isolates of the causal pathogen
Background: Frogeye leaf spot (FLS) has been a significant disease of soybean across the southern half of the U.S. for many years, and in the past few years has been increasing in distribution and severity in Minnesota. Additional information on its distribution in Minnesota and its sensitivity to fungicides that could potentially be used to manage it.
Goals and Approach/Methods: A. Determine the distribution of frogeye leaf spot in MN. Collect soybean leaf samples with symptoms typical of Frogeye leaf spot from fields across Minnesota and confirm that the FLS pathogen Cercospora sojae is associated with the symptoms. Leaf samples with symptoms of FLS will be collected from fields where symptoms appear and taken to my laboratory in St. Paul for analysis.
B. Evaluate efficacy of fungicides against the FLS pathogen (Cercospora) from soybean leaves in Minnesota. The FLS pathogen will be tested in a laboratory for sensitivity to fungicides (with a focus on the QoI fungicides) that could be used to manage it.

3. Conduct extension education and diagnostic activities that address important and unusual soybean disease problems in Minnesota.
Background: There is an ongoing need to develop and deliver disease management information and new research results for soybean diseases across Minnesota. In addition, unusual disease outbreaks occur in soybean fields across Minnesota each year for which specialized diagnosis and focused efforts are needed to help famers understand the problems and to identify and develop response and management strategies.
Goal A. Disseminate information, and teach and organize specialized meetings and workshops to address soybean disease information needs for soybean producers.
Goal B. Perform specialized diagnosis of unusual soybean disease problems from Minnesota and address problem fields when special disease situations occur.

Update:

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Update:

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Update:

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Project Title: Assessing Management Options and Inputs for Significant Soybean Diseases in Minnesota: Phase 2. May 2021-April 2022

Principle Investigator: Dean Malvick, University of Minnesota, St. Paul.

Objective 1. Evaluate inputs and tactics to manage SDS of soybean. SDS and BSR are often among the top 10 soybean diseases in the NC Region including Minnesota. SDS is spreading and becoming a problem in more areas, including areas where high levels of resistance in locally adapted varieties is limited or absent. BSR is widespread in Minnesota. Varietal resistance is used to manage BSR; however, resistance needs to be evaluated to incorporate and maintain resistance to this widespread disease.
Part A. Determine the benefits of seed treatments and resistant soybean varieties for management of SDS in different field environments. Studies were conducted in fields that were inoculated with the SDS pathogen and irrigated at Rosemount and Waseca, MN in 2021. The studies include two soybean varieties with different levels of resistance to SDS and five seed treatments (untreated, Acceleron base, ILeVO®+base, Saltro®+base, and Heads-Up®+base). The ILeVO and Saltro seed treatments both consistently reduced SDS relative to the untreated and base treatments in both locations. The Heads-Up treatment had inconsistent effects on SDS and yield. The results demonstrate the relative efficacy of the three seed treatments for SDS management, and follow a similar trend as seen in studies in 2020.
Part B. Evaluate varieties and soybean breeding lines for resistance to brown stem rot (BSR). Selected varieties and advanced breeding lines from the U of MN soybean-breeding program (n=20) were evaluated for resistance to the A and B types of BSR in a greenhouse. Resistance differed to the A and B types of the pathogen, with some varieties susceptible and some resistant to both types, and some with different resistance to the two types. We now have better BSR disease characterization for an important set of varieties and breeding lines.

Objective 2. Determine distribution of Frogeye Leaf Spot in Minnesota and evaluate fungicide activity against Minnesota isolates of the causal pathogen. Frogeye leaf spot (FLS) has been increasing in distribution and severity in Minnesota in the past few years. Additional information on the distribution of FLS and its sensitivity to fungicides was needed.
Part A. Determine the distribution of frogeye leaf spot in MN. Soybean leaf samples with symptoms typical of frogeye leaf spot were collected in 2021 from scattered fields in southern and central MN. The samples were taken to my laboratory in St. where we isolated and confirmed the disease and pathogen using standard pathogen isolation techniques and DNA sequencing.
Part B. Evaluate efficacy of fungicides against the FLS pathogen (Cercospora) from soybean leaves in Minnesota. We isolated the FLS pathogen from leaves collected from multiple field locations in MN. Isolates of the pathogen were sent to a cooperating laboratory (Dr. Carl Bradley’s lab) at the University of KY where they were tested for sensitivity to QoI (strobilurin) fungicides. All isolates of the pathogen tested from MN were resistant to QoI fungicides. This study confirms widespread distribution and resistance to QoI fungicides for the FLS pathogen across MN and a need to choose appropriate fungicides to manage FLS in MN.

Objective 3. Conduct extension education and diagnostic activities that address important and unusual soybean disease problems in Minnesota. There is an ongoing need to develop and deliver disease management information and new research results for soybean diseases across Minnesota. In addition, unusual disease outbreaks occur in soybean fields across Minnesota each year for which specialized diagnosis and focused efforts are needed to help famers understand the problems and to develop response and management strategies. Thus, we disseminated to address soybean disease information needs for soybean producers at in-person events across Minnesota. We also conducted specialized diagnosis focused on frogeye leaf spot, a significant root/stem disease outbreak near Waseca following heavy rains in July, as well as suspected charcoal rot, pod and stem blight, and BSR samples.

This proposal addresses the 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 and foliar diseases. This project focuses on stem and root diseases of soybean, primarily sudden death syndrome (SDS), brown stem rot (BSR), and frogeye leaf spot. These diseases limit yields in fields across Minnesota and are generally difficult to manage. SDS is a significant disease in Minnesota where it is spreading and causing more problems in areas where it has not before. Frogeye leaf spot has long been a significant disease across the southern half of the U.S., and has been increasing in Minnesota and nearby states. BSR is a common across Minnesota, and is a significant recurring problem that requires continued management. The goals of this project are to evaluate the value of seed treatments and resistant varieties for managing SDS and BSR, to clarify the distribution and fungicide resistance of frogeye leaf spot, and to conduct outreach and disease diagnosis. 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.