For the most part, cooperative weather has dealt a lot of potentially positive outcomes, with one notable exception in soybeans – sudden death syndrome (SDS).
"SDS is a big problem this year," says University of Missouri Extension plant pathologist Laura Sweets.
Sweets isn’t alone in her observations. Rampant reports have been popping up all over the Midwest the past several weeks. Because this disease appears in fields with high soil moisture, this year’s wet, cool spring set the stage for favorable SDS conditions in many areas.
According to Tim Jordal, product and agronomy manager with Great Lakes Hybrids, farmers just now seeing symptoms may not realize the problem has already been building for several months.
"It is a very slow growing fungus and takes a considerable about of time to appear," he says. "While symptoms usually appear in mid to late August, SDS actually infects the soybean plant quite early in the season usually in early May."
According to Purdue University, younger plants can show symptoms of SDS in rare circumstances, but typically the damage isn’t visible until flowering or later in the season. Symptoms begin with a mottling and crinkling of leaves. Later, major leaf veins turn yellow before dying and turning brown. Roots will lack the vigor of healthy plants and sometimes be rotted.
SDS is also sometimes mistaken for brown stem rot. Purdue recommends splitting the lower stem of symptomatic plants to determine which fungal disease is present. Brown stem rot can cause internal stem browning, resulting in a dark brown discoloration of the pith at the lower nodes of the plant. In contrast, the pith of plants affected by SDS will remain white, while the tissue below the epidermis will have brown to gray discoloration present.
Damage is often heightened in fields that also have high soybean cyst nematode (SCN) populations. Yield losses vary according to severity, but reports of 20% loss or greater is not uncommon. Add in the fact that no seed treatment or foliar fungicide can control it, and it’s a very tough – but not impossible – disease to manage, Jordal says. He recommends starting with a later planting date and using varieties that have good SCN tolerance.
"Other methods of preventing SDS are to minimize the effects of compaction by utilizing deep tillage and avoiding tillage or wheel traffic when soils are wet," he says. "Improving drainage will also reduce the risk of SDS."
Sweets encourages producers to note where SDS was found this year so they can put together a strong preventative management plan for 2015.
In the video below, Damon Smith, an Extension field crops pathologist for the University of Wisconsin-Madison, walks through additional advice for scouting for and identifying SDS.
To continue the conversation about SDS, see what other farmers are saying in the AgWeb Crop Comments and discussion forums.