DES MOINES, Iowa – Soybean growers across the South and much of the Midwest may be seeing signs of sudden death syndrome, a soil-borne disease that infects soybean fields and cuts into yields.
Checking for the disease now – in August and September – can help growers build a plan of defense against the disease next year.
According to Steve Butzen, agronomy information specialist with Pioneer Hi-Bred International, growers can minimize the potential for soybean yield reduction from SDS in high-risk fields by selecting tolerant varieties and following good management practices.
Understand the problem. “By taking the time to manage SDS-prone areas, you can improve your chances of successfully growing soybeans in potential risk areas,” Butzen said.
“The key is understanding how the problem can occur and then doing your best to manage against it.”
Sudden death syndrome is most common when soybeans are exposed to cool, moist soils early in the growing season. Early-planted soybeans are often at risk. Soil that is compacted and poorly drained also contributes to the problem.
About the disease. SDS attacks soybean roots early in the growing season. The Fusarium solani fungus that causes SDS survives in crop debris in the soil.
The organism enters roots through wounds caused by soybean cyst nematode (SCN), insect feeding or mechanical injury.
A toxin produced by the fungus eventually moves through the plant, causing above-ground symptoms, including yellow or brown leaves with green veins, premature leaf drop, flower and pod abortion and lack of pod fill.
Leaf symptoms of SDS are similar to those of brown stem rot (BSR) and stem canker.
Look for signs. To distinguish SDS from the other two diseases, first examine the outside of a stem. Brownish-black sunken lesions are signs of stem canker.
If no lesions are present, split the bottom eight inches of the stalk. The pith or inner core of the stem will be white, and the surrounding cortex will be grayish brown if SDS has infected the plant. In contrast, BSR demonstrates dark-brown pith with a green cortex.
Butzen recommends growers scout fields in August and September to determine the extent of the problem.
Identify suspect plants based on leaf and whole-plant symptoms and then check stems and roots to distinguish SDS from other soybean diseases.
Minimize damage. While SDS is a difficult disease to manage, there are several varietal and cultural practices that can help minimize damage to soybeans in coming seasons:
* Plant at-risk areas to tolerant soybeans. A number of new Pioneer