Michigan soybean growers had no shortage of challenges this summer, from dry midseason conditions to soybean aphid infestations.

One additional phenomenon that growers reported near the end of the season was stems that remained green long after the pods and seeds had matured.

According to Mike Staton, Michigan State University (MSU) Extension educator and Soybean 2010 coordinator, this is the classic symptom of green stem disorder, a condition first detected in 1974 in Kansas.

“The green stems may or may not contribute to yield losses,” Staton says. “There can be higher shatter losses when combining due to harvest delays or because those green stems are tougher to cut.”

The cause of green stem disorder is uncertain despite intensive research at several universities. Plant viruses, low soil moisture and insect damage are commonly cited as potential contributors.

Yet, the most likely cause of the widespread occurrence of green stem in Michigan this season was the lack of rain and dry soil conditions, says Kurt Thelen, MSU Extension field crop specialist.

The drought caused the plants to abort pods early in the growing season. Later in the season, when the rains finally came and growing conditions improved, there were not enough pods on the plants to use the sugars produced by photosynthesis. Those sugars accumulated in the stems, producing the green stem disorder.

Researchers at the University of Wisconsin and Ohio State University have shown that soybean varieties vary in their susceptibility to green stem. Farmers who had significant problems with the disorder in 2007 can use that information to limit future problems.

“Soybean growers who noticed green stems and had reduced yields this year should go through their records to determine which varieties exhibited the most severe green stem disorder and avoid planting these varieties in fields where moisture stress is likely to occur in the future,” advises Staton.

MSU and the Michigan Soybean Promotion Committee will continue to research green stem to find answers to the questions this phenomenon generated this fall. Soybean producers can learn more about green stem by participating in regional corn and soybean research updates and Soybean 2010 educational programs.

For more information about improving Michigan’s soybean crop, visit the Soybean 2010 Web page.

Source: Michigan State University Extension

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