Sudden death syndrome may impact soybeans

Yellow spots between leaf veins is an early symptom of sudden death syndrome.

WAHPETON, N.D. — A disease new to Richland County could have negative impacts on local soybean production.

Agronomists and agriculture agents advise farmers to watch for warning signs of sudden death syndrome. Common in southern Minnesota and South Dakota, the disease has symptoms and pathogens which correspond with plant samples taken from Richland County in 2018.

“It’s not something that we’ve detected in North Dakota until last year,” said Chandra Langseth, agriculture and natural resource agent for the NDSU Extension of Richland County.

Sudden death syndrome is commonly observed in a crop’s leaves. Yellow spots between leaf veins, or interveinal chlorosis, is an early symptom. The lesions may expand and turn brown while the spots expand between veins, Crop Protection Network reported. This condition is known as interveinal necrosis.

“As the disease progresses, leaves die and prematurely fall from the plant, while petioles remain attached to the stem,” Crop Protection Network reported.

Symptoms are similar to those found with diseases like brown stem rot, Langseth said. Because of this, diagnosis of sudden death syndrome requires thorough investigation. Plant samples taken in Richland County have been extensively tested.

“They have been unable to isolate the particular pathogen that causes sudden death in that plant,” Langseth continued. “We are pretty certain that (disease) is what was found in Richland County.”

Additional tests are needed before sudden death syndrome is officially announced.

“In North America, the fungus ‘fusarium virguliforme’ causes SDS,” Crop Protection Network reported. The presence of other pathogens, such as soybean cyst nematode (SCN), can also exacerbate disease.”

Pathologists from North Dakota State University surveyed hundreds of fields, largely in eastern North Dakota, in 2018. Plants with typical sudden death symptoms were identified in central Richland County. Samples from that field and other fields in the area were taken and continue to be tested.

“We start to see the symptoms in late July and early August, so it’s a good opportunity to talk about this now,” Langseth said. “Affected plans look pretty much healthy until this point. It starts minor and becomes severe.”

It is uncertain how sudden death syndrome pathogens arrived in Richland County.

“This is a residue-borne disease, which can move with soil and plant residue. Other diseases we’ve seen are moved with equipment or through soil erosion. With sudden death, we’re unsure how long the pathogen’s been here and where it came from,” Langseth said.

Yield losses due to sudden death syndrome can be highly variable and depend on several factors, according to Crop Protection Network.

“If symptoms develop later in the season, or weather is not conducive for disease development, yield losses can be minimal,” the organization stated.

An entire field is rarely lost, Crop Protection Network continued, because sudden death syndrome often occurs in patches.

“In general, once diseases are seen, it is too late to treat them. Right now, it’s about identification and management for the future,” Langseth said.

Should a farmer find sudden death syndrome symptoms in their soybean crop, the common course of action is to work with agronomists and agents to establish a course of action for future years.

Sudden death syndrome is considered typically worse when it occurs in an area where the planting season was cool and wet. Richland County experienced those conditions this year, Langseth said.

“This is a ‘good year’ for scouting for symptoms,” she explained. “We’re likely to see them this year rather than other years.”

For additional information, contact the NDSU Extension’s Richland County office.

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