Green Stem Syndrome Is Showing Up In Mature Soybean Fields In Southwest Missouri

LAMAR, MO.
   Jill Scheidt, agronomy specialist with University of Missouri Extension, is reporting seeing a lot of fields in southwest Missouri with Green Stem Syndrome.
   “Normally, when a soybean plant matures, it drops its leaves and stems lose their green color. Soybean plants affected by Green Stem Syndrome will not dry down properly, and seed may mature before the stem turns brown,” said Scheidt.
   The cause of green stem syndrome is unknown but attributed to many different causes like viruses, low soil moisture, potassium deficiency, soybean population density, genetic mutations in soybean plants, and insect damage.
   Reduced pod number during the full seed stage is an associated cause because carbohydrates and nitrogen remain in the stem and roots and appear to have a role in retention of green stems.
   “There were above threshold levels of green stink bug this year,” said Scheidt.
   When green stem syndrome is triggered by green stink bug feeding, management of the insect may be helpful. Treatments must be applied when leaves and pods are green, and feeding is taking place.
   “When green stem syndrome results from viral infection, management is difficult. Managing viruses usually requires controlling the vector of the virus,” said Scheidt.
   According to Iowa State University, lower fall humidity, and higher fall temperatures can be associated with Green Stem Syndrome – they can lead to faster dry down for the grain, but not stems.
   Scheidt does not recommend delaying harvest to allow green stems to dry sufficiently. “Delaying harvest by 3-4 weeks, usually results in exceptionally low seed moistures and increases shattering and harvest losses. So plants affected by green stem syndrome should still be harvested when soybeans reach 13 percent moisture, even if the stems are still green,” said Scheidt. ∆