Green stem syndrome prevalent in 2010
Despite record soybean production in 2010, yields could have been even better, says a University of Missouri Extension specialist. One reason was green stem syndrome, or GSS.
“Normally, when a soybean plant matures, it drops its leaves and the stems lose their green color,” says Travis Harper, an agronomist based at Clinton. “Soybean plants affected by GSS will not dry down properly and seed may mature before the stem turns brown, or even before all leaves are shed.”
Typical soybean production strategies call for harvesting soybeans after leaves have dropped and stems have lost their color. This may never happen in fields affected by GSS. Yield loss often occurs when mature soybean pods shatter as harvest is delayed.
GSS is quite common, and typically occurs throughout the United States every year.
• Soybean yields are held back by green stem syndrome.
• GSS affected many soybean fields in Missouri in 2010.
• To prevent GSS, growers are urged to select disease-resistant varieties.
“What was unusual this year was that GSS was present in such a large geographical area, and that it affected a large majority of soybean fields,” Harper says.
GSS is thought to be caused by a combination of disease (usually viral), insect damage and environmental stress (typically drought) during the reproductive stage of the plant. On their own, disease, insects and environmental stress rarely cause widespread green stems.
“It was a unique combination of these that led to entire fields being affected by GSS,” he says.
The most common insect culprits are stinkbugs and corn earworm. Flights of corn earworm moths were extremely high in 2010, making them the most likely insect culprit.
It’s not always possible to prevent GSS, but there are things producers can do to make it less likely to occur.
The first is to select soybean varieties that are resistant to viruses and other diseases. The second is to take actions to keep pod- and seed-feeding insects below economic thresholds. Though trying to prevent drought stress on nonirrigated soybean fields is difficult, producers might consider adjusting their planting dates and variety maturities to avoid drought stress.
The unique combination of conditions that led to widespread GSS in 2010 is unlikely to occur in 2011, Harper notes.
“However, GSS will occur in fields again in the future — whether in localized spots or across entire fields.”
The best management practice is to harvest once seed moisture content reaches 13%, no matter what the stems and leaves of the plants look like, Harper advises.
Source: University of Missouri Extension
This article published in the January, 2011 edition of MISSOURI RURALIST.