Developing an integrated management and communication plan for soybean sudden death syndrome

Objectives:

• Determine how seed treatments, in-furrow, and foliar fungicides will affect soybean sudden death syndrome (SDS).
• Evaluate if soybean cyst nematode reproduction affects SDS development.
• Study how cultural practices affect inoculum levels and SDS development.
• Determine a Return on Investment (ROI) for SDS management strategies.
• Communicate research results with farmers, agribusinesses and other soybean stakeholders.

Impacts:

• Improved SDS management recommendations: Identified effective seed treatments – especially fluopyram (ILeVO) – reducing foliar SDS by 35% and increasing yield by ~4.4 bu/ac, helping growers make more profitable decisions.
• Strengthened understanding of SDS–SCN interaction: Demonstrated that SCN resistance breakdown (PI88788) is strongly linked to increased SDS severity, reinforcing the need for SCN management as part of an SDS program.
• Evidence-based ROI for growers: Showed that lower seeding rates (103,000–112,000 seeds/ac) with ILeVO provide the highest profitability and lowest economic risk, improving input efficiency.
• Validated integrated management practices: Confirmed that resistant cultivars, seed treatments, SCN management, and cultural practices work synergistically, forming the foundation of an effective SDS IPM plan.
• Enhanced disease risk knowledge: Demonstrated that environmental conditions and planting date have major influences on SDS development and the performance of seed treatments, helping refine planting-time risk assessments.
• Advanced diagnostics and research capacity: Identified the most accurate qPCR method for detecting Fusarium virguliforme in plant and soil samples, improving research precision and future monitoring efforts.

• Clarified glyphosate’s role: Multi-year data showed minimal impact of glyphosate on SDS, shifting focus to more meaningful risk drivers such as weather and soil conditions.
• Supported cross-border extension impact: Communicated results through extension events, articles, and social media across Ontario and the U.S. Midwest, increasing farmer awareness and accelerating adoption of proven SDS management strategies.
• Strengthened multi-state collaboration: Leveraged a multi-institutional Network (OMAFRA, ISU, MSU, UW-Madison) to produce coordinated, region-wide recommendations benefiting soybean growers across the entire North Central region.
• Enabled proactive management in emerging areas: Provided early education for newly affected regions, helping reduce risk as SDS moves into previously unaffected parts of Ontario and the U.S.

Project Overview:

Sudden death syndrome (SDS) is an annual threat to soybean in most of the North Central region of the U.S. and southwestern Ontario. In 2014, this disease alone caused an estimated loss of nearly 64 million bushels in the U.S. and Ontario, valued at approximately $617 million. The foundational management strategy for SDS (caused by Fusarium virguliforme) in soybean is using resistant cultivars. We have been evaluating industry standard susceptible and resistant cultivars in the North Central region for the last five years and resistant cultivars have shown less disease and more yield than the susceptible cultivars in many evaluations. However, in years when environmental conditions are favorable for disease development, like in 2014, it is evident that resistance alone does not provide adequate disease control or reduce farmer risk sufficiently. As the disease continues to spread into new areas, we have an opportunity for early education and improved awareness of the importance of using an integrated management program for SDS. Thus, the main goal of this project was to investigate management options that will help ensure resistant cultivars will be as effective as possible in years when conditions are highly conducive for SDS.

Results:

From our previous SDS management project, we finished a study looking at the effect of SCN management on SDS severity and a manuscript has been published (Plant Disease, Vol. 100, No. 8 August 2016, APS Press). In summary, SCN resistance played a critical role on SDS development. Fall season SCN population density and SDS were positively correlated. We found PI88788 resistance source has been broken by nematode populations in all of the tested sites in the North Central region and Ontario. Cultivars with no resistance to SCN had the highest disease and lowest yield. Even though the PI 88788 type resistance was not holding up, any type of SCN resistance led to greater yields, lower SDS, and lower SCN reproduction than the cultivars with no resistance.

We also established field trials to test the effects of fungicide treatments on SDS, and we identified differences in efficacies among the products in the previous projects. Fluopyram (ILeVO, Bayer CropScience) seed treatment was found to effectively manage SDS and increased yield in our previous evaluations. The manuscript has been published in Plant Disease (Plant Disease 100:1339-1350). We also complied data from multiple locations evaluating ILeVO seed treatment for SDS management and yield response to the seed treatment using a meta-analysis approach. A manuscript has been published in Plant Disease (June 2018, APS press). In summary, we found a 35% reduction in foliar disease and 4.4 bushels/acre (7.6%) increase in yield for fluopyram-amended seed treatment relative to commercial base seed treatments without fluopyram. However, the disease severity, planting date, geographical locations, and weather conditions influence the efficacy and yield benefits of the IleVO.

We were able to build on the investment made in the previous years and also add new angles of SDS management using other management approaches. This included completed field experiments for a study coordinated by Dr. Shawn Conley (University of Wisconsin) to investigate the economic risk and profitability of seed treatments on soybeans planted at different populations. A manuscript has been published in Crop Science (Vol. 57 No. 4, p. 2251-2262) and an extension publication was posted online. Briefly, planting population does not seem to have effect on SDS but analysis of economic risk and profitability of seed treatments with different seeding rates suggested that the lowest economic risk and highest average profit with ILeVO seed treatment was obtained when seed rates were lowered to 103,000 to 112,000 seeds/acre. From our previous SDS management project we identified the most effective quantitative PCR technique for identifying F. virguliforme in soybean plants and in soil. This allowed us to evaluate the effects of management practices on inoculum levels in the field and F. virguliforme levels in soybean plants.

External Funding Partners (for the Ontario portion of the project):

Growing Forward 2, a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of Growing Forward 2 in Ontario.

Project Related Publications:

Conley, S. P., Kandel, Y. R., Shaner, G. E., Esker, P. D., Smith, D. L., Mueller, D. S., Chilvers, M. I., Tenuta, A. U., & Wise, K. A. 2017. Economic risk and profitability of soybean seed treatments at reduced seeding rates. Crop Science. 57(4): 2251–2262.

Kandel, Y. R., Bradley, C. A., Wise, K. A., Chilvers, M. I., Tenuta, A. U., Davis, V. M., Esker, P. D., Smith, D. L., Licht, M. A., and Mueller, D. S. 2015. Effect of glyphosate application on sudden death syndrome of glyphosate-resistant soybean under field conditions. Plant Dis. 99:347-354.

Kandel, Y. R., Wise, K. A., Bradley, C. A., Chilvers, M. I., Tenuta, A. U., Mueller, D. S., and Hartman, G. L. 2016. Effects of seed treatments on sudden death syndrome and yield of soybean. Plant Disease. 100(7): 1339–1350.

Kandel, Y. R., Mueller, D. S., Wise, K. A., Chilvers, M. I., Tenuta, A. U., Smith, D. L., and Hartman, G. L. 2016. Impact of planting date and seed treatment on sudden death syndrome and yield of soybean. Plant Disease. 100(9): 1735–1743.

Kandel, Y. R., Wise, K. A., Mueller, D. S., Chilvers, M. I., Smith, D. L., Tenuta, A. U., and Hartman, G. L. 2017. Effects of soybean cyst nematode resistance on sudden death syndrome and soybean yield. Plant Disease. 101(12): 2137–2143.

Kandel, Y. R., Mueller, D. S., Wise, K. A., Chilvers, M. I., Smith, D. L., Tenuta, A. U., and Hartman, G. L. 2018. Meta-analysis of fluopyram seed treatment efficacy on sudden death syndrome and yield of soybean. Plant Disease. 102(12): 2545–2552.