Crop residues are typically conserved in the field following harvest to improve soil health. However, such residues allow microorganisms to survive between cropping seasons and cause plant diseases. For example, on wheat, the fungus causing tan spot (Adee and Pfender 1989) has been shown to infect the crop planted after wheat if wheat residues are left in the field following harvest. The 2022 USDA Census of Agriculture reported a 1% increase in no-till acreage nationwide compared to the 2017 census (USDA NASS 2024). In no-till systems, post-harvest residues generally accumulate up to 10 Mg ha-1. Because of North Dakota’s long winter conditions, the decomposition of residues can be limited, providing conditions for microorganisms that cause diseases to survive between cropping seasons. Although cultural management practices have been explored for other crops (e.g., wheat), we have limited data on the impact of such practices in soybean on the incidence of root rot pathogens, such as Fusarium and Pythium, which have a broad host range. For the proposed study, we will establish trials at NDSU REC in Carrington in 2025 to evaluate the impact of tillage and residue management on root rot caused by Fusarium and Pythium under North Dakota soil conditions. The findings from this study will provide farmers with information on whether tillage and residue management regimes can reduce the levels of Fusarium and Pythium (syn. Globisporangium) causing root rot in the soil.

Objective 1. Evaluate the effect of tillage practices on the species diversity and abundance of Fusarium and Pythium.
Objective 2. Determine the effect of crop residues (e.g., corn stover) on the species diversity and abundance of Fusarium and Pythium.

• A protocol will be developed to screen soybean varieties for susceptibility to SCN and SDS, using isolates from North Dakota.
• We will create a comprehensive overview of the interactions between SCN and SDS, highlighting knowledge gaps and areas for further investigation in two peer-reviewed manuscripts.
• Extension materials will be prepared for soybean farmers, emphasizing the relationship between SCN and SDS based on our research findings.

Soybeans are an important crop for farmers in North Dakota. However, SCN and SDS threaten soybean yields, and in counties where both SCN and SDS are prevalent, yield losses can be severe, making it essential to develop effective management strategies for these pathogens. This research focuses on understanding the interactions between SCN and SDS, providing valuable insights into how these pathogens jointly affect soybean health. With this knowledge, more targeted and effective management strategies can be developed to address both pathogens simultaneously. The goal of this research is to help farmers implement precise control measures that will reduce crop damage, minimize yield losses, and improve profitability. Additionally, the research could contribute to the broader understanding of pathogen interactions in agricultural systems, benefiting soybean growers beyond North Dakota.