Research Highlights

Uncovering the Drivers of Soybean Green Stem Disorder

By Carol Brown

Farmers and scientists know how to manage or reduce the severity of many soybean issues, but green stem disorder is still a puzzlement. Researchers are actively studying how to reduce it or prevent it from happening.

Green stem disorder, also called green stem syndrome, is when parts of the soybean plant stay green through maturity and harvest. It usually has a green stem that is sometimes accompanied by thick, green, leathery leaves remaining at harvest time or until a frost or freeze kills the plant. 

Through a new project funded by the Minnesota Soybean Research and Promotion Council, agronomist Seth Naeve is delving into this disorder. The Minnesota extension soybean specialist will look at which crop stressors trigger green stem disorder and when the stressors activate it. 

“The disorder is common in all soybean growing regions, and there aren’t definitive causes for it,” Naeve says. “The pattern by which green stem disorder shows up is variable, sometimes with random plants throughout the field, more often at field edges or consistently across a field.”

Researchers believe that stems remain green at the end of the growing season because there is too much energy in the plant and not enough “sink,” or pods for it to go into, leaving all that energy stuck in the stem, Naeve says. Plants with this disorder don’t flow through the combine as well, and there could be some discoloration or staining of harvested seeds.

Naeve’s research project will focus on understanding the sensitivity of soybean stress and when those stressors most affect the plant, potentially triggering green stem disorder. 

“In southern states, there can be a direct correlation of crop stress and green stem disorder, which may include things like pod loss or stink bugs feeding on the soybean seeds. But in the North, we still have green stem disorder without obvious stressors like insect pressure,” he comments. “We’re interested in specific timings of individual stresses and how they can reduce soybean seed number, weight and yield, and when might those factors drive green stem disorder.”

Naeve and his research team are looking at specific stressors including reduced sunlight and drought. Lack of sunlight stresses the plant as it can’t access needed nutrients. The team will shade the soybeans at various growth stages over a 10-day period to create low light stress conditions. They will also use an irrigated research location with controlled watering to measure drought stress over a certain time period. The team will observe if and when green stem disorder occurs under these stressors. 

“Specific causes of green stem disorder vary from location to location as well as from year to year. We’re hoping to find connections between stress timing and when that can trigger the disorder as well as how severe the disorder is with these stressors,” says Naeve.

Shedding light on how green stem disorder comes about could help researchers learn how to reduce its occurrence. This, in turn, can help farmers toward a smoother harvest and reduced yield loss. 

Other resources:

Green Stem Disorder – SRIN information page

Published: Nov 6, 2023