Research HighlightsManagement Practices Show Potential to Reduce Impact of Sudden Death Syndrome
By Laura Temple
What leads to outbreaks of sudden death syndrome, or SDS, in soybeans?
David Langston, professor and extension plant pathologist for Virginia Tech, asked this question as his role shifted to include investigating soybean diseases. With soy checkoff support from the Virginia Soybean Board, he began conducting survey work and treatment trials for both SDS and nematodes in 2021.
“These efforts focused on key soybean challenges that Virginia soybean growers need to manage,” Langston says. “Ongoing research helps identify recommendations and points to future research needs.”
To better understand SDS, Langston’s team gathered plant samples, photos and management practice information from every Virginia field where farmers or consultants reported the disease to a county extension agent.
During this survey, symptoms of SDS typically didn’t appear until soybeans reached the R6 growth stage, the start of pod fill. In affected fields, his team focused on the roots of dying plants, which had systems only half as developed as healthy plants. Some diseased plants also showed vascular discoloration in leaf veins and stems.
“The main thing we observed is that SDS appears almost exclusively in early planted soybeans,” Langston says. “Typically, we received reports of SDS in fields planted from late-March to mid-April, even though symptoms didn’t show up until late August, when the stress of beginning pod fill was too much for damaged root systems.”
He explains that the soilborne pathogen Fusarium virguliforme, which causes SDS, infects roots during cool, wet conditions.
“Those conditions were common in 2021, and we received many reports of SDS,” he says. “Under the much drier conditions of 2022, farmers and consultants reported very little SDS.”
With nationwide planting date research showing the yield benefits of planting early, Langston understands the trend toward early planting. He sees the threat of SDS as one negative that needs to be managed for farmers to reap the full value of early planting.
In cool, wet spring conditions, he recommends either planting later or using a seed treatment with activity against Fusarium to avoid SDS. Though he hasn’t done seed treatment research himself, published data shows that some treatments can reduce symptoms and protect soybean yield.
Langston’s survey found SDS in some soybean varieties characterized with resistance to the disease in 2021, though it was less common than in susceptible varieties.
“I’ve planned trials to study varieties with SDS resistance and planting dates in 2023,” he says. “However, what we learn will depend on weather conditions and SDS pressure.”
He points out one other factor farmers can manage to reduce the impact of SDS.
“In our survey, 50% or more of SDS outbreaks and severe outbreaks occurred in fields with high populations of soybean cyst nematode and root-knot nematode,” he explains. “SDS and nematodes often go together to form a disease complex. That has been documented with soybean cyst nematodes. We’ve observed similar tendencies with root-knot nematodes, though that hasn’t been published. I plan to do the greenhouse work needed to prove a similar relationship between SDS and that species.”
He explains that nematodes feed on soybean roots, and those open wounds make the plants more susceptible to other soilborne diseases. His additional research in this project focused on understanding and managing yield-robbing nematodes in soybeans.
Sudden Death Syndrome – SRIN information page
Published: Mar 13, 2023
This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.