Project Details:

Multi-dimensional approaches for improved productivity, sustainability, and management of major soybean diseases in the North Central US

Parent Project: This is the first year of this project.
Checkoff Organization:North Central Soybean Research Program
Categories:Soybean diseases
Organization Project Code:
Project Year:2022
Lead Principal Investigator:Damon Smith (University of Wisconsin)
Co-Principal Investigators:
Daren Mueller (Iowa State University)
Rodrigo Borba Onofre (Kansas State University)
Christopher Little (Kansas State University)
Martin Chilvers (Michigan State University)
Horacio Lopez-Nicora (Ohio Agricultural Research and Development Center)
Mitchell Roth (Ohio Agricultural Research and Development Center)
Darcy Telenko (Purdue University)
Febina Mathew (South Dakota State University)
Ahmad Fakhoury (Southern Illinois University)
Jason Bond (Southern Illinois University at Carbondale)
Dean Malvick (University of Minnesota)
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Information and Results

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Project Summary

Soybean is a major field crop in the North Central region and the entire United States. Soybeans are susceptible to an array of disease-causing microbes that can result in significant costs for the farmer and to the environment, due to the application of pesticides to control them. A major premise of the study of plant pathology is that for diseases of plants to occur there must be the presence of a virulent pathogen, a susceptible host, and an environment that is favorable for disease development (host, pathogen, and environment are the legs of the triangle). This last factor stands to be a major driver of plant disease. In fact, the environment can influence when and where pathogens will cause disease problems and a changing climate can result in the occurrence of new diseases affecting soybeans.

Recent changes in weather conditions have led to the re-emergence of some diseases in the North Central region or the expansion of diseases into the region. For example, frogeye leaf spot (caused by the fungus Cercospora sojina) has been an increasing problem in the upper Midwest. In recent years this pathogen has become a more significant issue, causing severe epidemics in states where it traditionally had not been a problem. It is thought that due to climate change, the fungus can survive warmer winters (Roth et al., 2020). In addition, warmer growing seasons result in wetter growing seasons, meaning wind-dispersed rain, and splashing rain, are prominent for dispersal of the frogeye leaf spot pathogen. High humidity also makes for conducive conditions for disease development and high severity.

Cropping systems also have changed leading to increased continuous soybean production and no-till cropping systems. This leads to larger proportions of pathogen inoculum surviving in soybean fields. These changes in production practices over the past decade combined with challenging weather events, require creative solutions for sustainably managing these diseases.

Seedling Disease Complex. Water molds (> 40 species of Pythium, and Phytophthora sojae, Phytophthora sansomeana), and true fungi (Fusarium spp. (including SDS), Macrophomina phaseolina (charcoal rot), and Rhizoctonia solani) have each alone or in combination contributed to stand loss as well as replanting. Much of the research to date has focused on each of these individually, but based on our isolations and diagnostics, it is clear that an approach that focuses on managing these diseases as a complex throughout the soybean growth cycle from planting to harvest is sorely needed. Performing trials with uniform protocols across states, looking for products (seed treatments) that might balance management of more than one pathogen of seedlings is desired.
Foliar Pathogens and Fungicide Resistance. Frogeye leaf spot, caused by Cercospora sojina, has become re-established and is expanding in the North Central Region, and there is little information on the best fungicide timing, most effective fungicides, or the best way to scout to assess the need for a fungicide application (e.g., by foot, drone, or airplane). Specifically, at each growth stage, what levels of disease contribute to yield loss for each maturity group? Experiments to assess if this fungus overwintered were completed in Ohio and Illinois, but not in regions further north. A predictive tool is needed to determine which years C. sojina will overwinter, the inoculum load in the spring necessary to begin an epidemic, and under what conditions a fungicide spray is warranted.

More importantly, is there a continued shift in this fungal pathogen population towards QoI resistant strains in the North Central Region? Does this shift in fungicide sensitivity indicate a change in winter survival? What is the virulence spectrum of these strains? Are the soybean cultivars and germplasm for this region resistant to these strains? Recent evidence from several team members also suggests that the fungus that causes brown spot is not responding to QoI fungicides as it once did. There are also more reports of subtle shifts towards resistance in some fungi to the triazoles, plus the push by some in industry for half rates of fungicides. The role that this half fungicide rate approach will have on the development of resistance as well as fungicide efficacy in low, moderate, and high disease environments is unknown. Monitoring fungicide sensitivity and recommending appropriate timeliness of fungicide applications are critical for continued successful management.

Stem Diseases and Seed Quality. Northern and southern stem canker, pod and stem blight, brown stem rot, and a various array of other diseases affect seed quality in the North Central Region. The basic pathology and disease cycle of these diseases are largely unknown in the North Central Region. These diseases have long been issues in this region. The distribution of the two stem canker diseases (southern and northern) needs further geographic clarification since resistance varies between these two diseases. Additional immediate and important questions for this complex are: Will southern stem canker replace northern stem canker? Will southern stem canker establish and survive in the soil or on weedy hosts in the region? How often does brown stem rot play a role in the stem disease complex? What resistance levels are readily available to these diseases in the Midwest germplasm? Will fungicides limit or control this complex of organisms? Symptoms of these stem diseases, SDS, stem canker, and brown stem rot are all very similar (especially from roadside truck surveys). Can scouting be improved for accurate sampling and or predictive tools developed for in-field management?

Develop predictive models and model validation. Several soybean disease prediction tools currently exist or are being developed. For example, the Sporecaster prediction tool (Willbur et al., 2018 a and b) was developed for white mold and supported by NCSRP and state-level checkoff funds. Models like this use weather information incorporated into mathematical or statistical models to calculate the risk of disease development and help guide timely fungicide applications. These tools can be adapted and validated for other diseases of concern. Diseases continuing to increase in affecting a large number of acres include frogeye leaf spot and stem canker. The Sporecaster framework is flexible and adaptable to various diseases and the delivery of the tool can be done easily placing the tool in the hands of farmers and consultants.

The impact of new cropping systems on soybean diseases throughout the region. Changes in production systems, seeding rates, cover crops, strip tillage, new bio-active treatments, not to mention sugar, have been incorporated into farmer practices. How and if these practices and products favor or inhibit soybean pathogens is unknown. Fertility and the influence of fertility level on soybean diseases isn’t well understood. Understanding fertility influences on disease will be important for sustainably managing new and emerging diseases into the future.

Overall Goal: To develop improved management strategies, and communication of those strategies, for the sustainable management of the major soybean diseases in the North Central U.S.

Project Objectives

Overall Goal: To develop improved management strategies, and communication of those strategies, for the sustainable management of the major soybean diseases in the North Central U.S.

Objective 1: Conduct multi-site-year product efficacy trials to develop a robust, non-partial dataset to educate and inform farmers and practitioners on the performance of disease control products available for soybeans

Objective 1a. Conduct uniform foliar fungicide trials that target a holistic approach to control white mold, frogeye leaf spot, and stem canker (Diaporthe diseases); find programs that might be able to cover these major diseases simultaneously.

Objective 1b. Conduct uniform seed treatment trials to target sudden death syndrome, brown stem rot, Phytophthora root rot, and Pythium root rot.

Objective 2: Conduct research and validation trials to develop and/or validate disease prediction tools or risk studies for major soybean diseases

Objective 2a. Develop a frogeye leaf spot model using the Sporecaster framework.

Objective 2b. Develop prediction tools for stem canker of soybean using the Sporecaster framework.

Objective 2c. Validate an existing soybean sudden death syndrome prediction tool for predicting risk of epidemics in soybean fields.

Objective 3: Develop improved understanding of the biology and epidemiology of emerging and re-emerging diseases of soybean in the North Central Region.

Objective 3a. Monitor for fungicide resistance in the frogeye leaf spot pathogen, Septoria brown spot pathogen, stem canker pathogens, white mold pathogen, Pythium species, and Phytophthora root rot pathogens.

Objective 3b. Develop a better understanding of how to improve seed health and quality with a focus on Diaporthe diseases (stem canker) and brown stem rot.

Objective 3c. Develop improved tools for frogeye leaf spot, sudden death syndrome, and brown stem rot management including fertility impacts on the disease, how rotations influence disease incidence and severity, and how new products like nano-fertilizers and other nanotechnology influence disease.

Objective 3d. Understanding the pathogen complex causing Cercospora leaf blight (CLB) in the North Central region. Conduct a survey in the NC region and understand the pathogen complex and how it relates to what has been identified in the south and mid-south.

Objective 4: Develop extension tools through state extension programs, Crop Protection Network (CPN) and Soybean Research and Information Network (SRIN).

Objective 4a. Use the efficacy information from objective 1a and 1b to inform and update fungicide efficacy charts annually for the Crop Protection Network.

Objective 4b. Communicate with farmers and agribusiness personnel through extension articles, videos, webinars, and field days.

Project Deliverables

The results of this research will be used to not only increase our understanding of the biology and epidemiology of various diseases on soybean, but will be used to formulate improved, modern, sustainable integrated management decisions for the major diseases of soybean in the North Central Region. Several important outcomes and deliverables will result from this research. These include:
- Companion extension publication detailing the foliar fungicide meta-analysis
- Development of new forecasting tools for frogeye leaf spot and stem canker
- Demonstration plots will be available for field days and other educational opportunities in the participating where integrated strategies for managing the major diseases of the North Central region will be showcased
- Fact sheets and publications will be generated using the most current information as a result of this coordinated effort (many of the personnel on this proposal have extension appointments in addition to their research appointments, and all personnel are well-versed in communicating their research to the public).
- Results of research will be presented at stakeholder meetings
- Blog articles will be written on extension personnel websites
- An electronic book will be developed for Sclerotinia stem rot management

Progress of Work

Final Project Results

Benefit to Soybean Farmers

Soybean farmers and agriculture scientists will benefit from this research by:
-Gaining an improved understanding of key, modern management strategies for diseases of soybean
-Improved management of soybean diseases resulting in improved yield and profitability
-Improved timing of necessary fungicide applications through use of the advisory tool will improve fungicide efficacy and disease control
-Reduced unnecessary fungicide inputs can be avoided
-A better understand of the breadth of fungicide resistance in soybean pathogen populations
-New and improved outreach materials will be developed, including updated web pages and handouts
-An electronic book will be developed to bring a quick, modern, usable reference into the hands of the next generation of farmers and scientists

Performance Metrics

- Peer-reviewed publications detailing the findings pertaining to fungicide resistance in the major pathogens of soybean in the North Central region
- A peer-reviewed publication and corresponding extension publication detailing improvements in the understanding of seed health in soybean as it relates to the Diaporthe diseases and brown stem rot
- Peer-reviewed publication detailing a comprehensive meta-analysis and economic analysis of the foliar fungicide data from objective 1a.
- Peer-reviewed publication detailing a comprehensive meta-analysis and economic analysis of the seed treatment data from objective 1b.
-A peer-reviewed publication and corresponding extension publication on results of the fungicide resistance screening
-Fact sheets and publications will be generated using the most current information as a result of this coordinated effort

Project Years