Research Highlights

Research Highlights
Studying the Connections Between Sudden Death Syndrome and SCN

Soybean plant with sudden death syndrome foliar symptoms. Photo: Daren Mueller, Crop Protection Network

By Carol Brown

Most farmers are aware of soybean cyst nematode as it is found in nearly every soybean-growing county in the United States. But sudden death syndrome is also a major yield-robbing soybean disease, and its impact is increasing across the country. Researchers continue to work to reduce the impact of both SCN and SDS — and some are digging deeper into the relationship between them. 

“The fungal pathogen Fusarium virguliforme causes sudden death syndrome,” says Febina Mathew, a crop pathologist at North Dakota State University. “It is an emerging problem in North Dakota; its presence was officially confirmed in 2018.”

Sudden death syndrome affects soybeans in two phases. The first phase is root rot, infecting soybean seedlings. Second is the foliar phase, exhibiting symptoms when soybeans are in the flowering stage and beyond. If Fusarium virguliforme is present in the soil, it needs cool, wet conditions to become active and grow. It then produces toxins that enter the roots and travel up the plant, causing discolored, dropping leaves and eventually death.

Mathew is leading a project, funded by the North Dakota Soybean Council, part of which is studying the interaction between Fusarium virguliforme and SCN.

“SCN is based on the Heterodera glycines, or HG, type numbered 1 through 7, which refers to the potential resistances it can overcome,” explains Mathew. “The type 2.5.7 is becoming prevalent in North Dakota. We will conduct greenhouse studies that look at the interactions between this HG type and Fusarium virguliforme to see if SCN presence can increase the disease severity caused by the Fusarium.”

Soybean cyst nematode. Photo: Sam Markell, The SCN Coalition

Susan Watkins, a soybean grower near Sutherland, Virginia, heads the United Soybean Board’s Health and Nutrition Supply Work Group, which concentrates on soil and plant health, and best management practices.

“SCN and sudden death syndrome are of concern for farmers,” Watkins says. “Both are yield robbers to a farmer’s bottom line. The need for more methods of control is critical to decrease the yield loss from these two issues, and USB is funding research projects for both.” 

Mathew is involved with these projects, as well as other projects funded by the North Central Soybean Research Program, including the exploration of cultivars that are resistant to Fusarium virguliforme and other pathogens, and evaluating the efficacy of seed treatments for SDS. The projects include corresponding research in Michigan, with field crops pathologist Martin Chilvers at Michigan State University leading the work.

“We know that soybean cyst nematode can exacerbate SDS development — we just don’t know how,” says Chilvers. “We are working to answer questions about their relationship. Although SCN and SDS exist independently, in previous field trials we mapped the presence of Fusarium virguliforme as well as soybean cyst nematodes. When they overlapped in the field, we saw worse SDS development.”

Through a project supported by the Michigan Soybean Committee, Chilvers is developing an SDS risk prediction tool based on soil sampling, similar to SCN identification methods.

“We hope we can use this risk indicator tool for both SCN and SDS,” Chilvers says. “A farmer or scout can send in a soil sample, and we would look for nematodes and also the levels of Fusarium virguliforme using a technique with DNA to essentially count the amount of Fusarium that are present.”

If one set of soil samples can determine the presence of both potential yield-robbers in a field, that can affect field-level management decisions. Farmers will be able to make informed choices such as selecting cultivars resistant to both SCN and SDS, and whether a fungicide treatment is necessary. 

“Farmers need to be proactive and incorporate measures in their practices to reduce these issues,” Watkins says. “If they aren’t addressed, it could lead to increased problems and continuous yield loss.”

Other Resources:

Michigan project: Soybean SDS and SCN management: Risk Prediction, Seed Treatments and Variety Screening

Published: May 29, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.