Green Stem Syndrome

Every few years, this topic resurfaces as a hot discussion topic. This year, with soybean harvest underway in certain regions of Dairyland Seed, it has once again become a subject of renewed interest.

What causes green stem syndrome? There are several possibilities. Each can be caused by different agents. This year seems to be more related to environmental conditions. Potential causes are mutated plants, environmental conditions, viruses, and insect feeding. 

Currently, there is still a bit of uncertainty as to the exact cause. It was originally thought that diseases such as pod mottle virus vectored by feeding from aphids or stink bugs could cause this issue. 

• Mutated or Rogue Plant Theory: This theory suggests that green stems can appear, but only on a few scattered plants. These plants have very few pods and very few beans per pod. This isn’t something you’d see across an entire field, but rather only a few scattered plants. 
• Virus Theory: Some universities have data suggesting the virus theory might not be accurate either.

• Environmental Conditions: Given this growing season, environmental conditions are most likely the case. If soybean pod set was less than we had plant resources for, and then we had great or very good conditions late season, we could get green stems. Basically, we have excess plant resources, and the plant stays green longer. Many agronomists refer to it as “sink and source.”  We have more “sources” (plant sugars etc.) than we have a “sink” (soybeans) for them to go. One example that supports this is a row where the planter had an issue, resulting in limited population. Those plants with less inter plant competition stayed greener for a greater period of time.