Green Stems In Soybeans?

It’s not uncommon to have spots or patches in fields that make harvest a challenge. Sometimes everything looks dry, but stems stay green. Pinpointing the ‘absolute’ cause of this issue commonly referred to as Green Stem Syndrome is difficult but likely has its origins in how the plant dries down.

As plants dry down naturally, nutrients in plant vegetative tissue (source) are shipped to the developing seed (sink). If there aren’t enough developing seeds to absorb it all, nutrients remain in stems (and maybe leaves), beyond the plant’s ‘normal’ maturity. While not always a yield robber, it can reduce harvest efficiency and potentially contribute to declining seed quality or dockage as well.

Potential contributors to green stem syndrome include:

• Disease: Bean Pod Mottle Virus, transmitted by the bean leaf beetle could reduce seed set.
• Insect: stinkbug feeding on pods/seeds can reduce seed load
• Genetics: plants predisposed to producing excess pods that might not always produce seed
• Fungicide: the delayed senescence sometimes associated with applications might be misidentified as green stem
• Weather: If we produce a large plant but weather inhibits pod set or fill, plants may not dry down normally

Finding more green stems than you’d like. Take a look at field patterns to see if the stressor can be identified. It’s not always possible to know for sure what might have caused the issue but understanding a little more about the why can give us a head start on next year.