Soybean Sudden Death Syndrome, the number two top yield-robbing disease for soybeans in 2014, threatens to severely diminish the gains in productivity soybean growers have come to expect from their crop. First seen in Arkansas during the early 1970s, SDS has quickly spread to most of the soybean growing areas in the Midwest and today shows no signs of slowing down.
Often appearing as an isolated spot within a field, SDS can expand rapidly to infect other areas. Because the pathogen overwinters in the soil, it can spread with each new season, especially under conditions of high soil moisture. Early symptoms range from mosaic patterns to a yellowing appearance between the veins, eventually turning to brown tissue and necrotic lesions. This reduces the ability of the plant to provide nutrients to promote pod fill, which results in aborted pods and reduced yields.
In 2014, SDS caused more than 60 million bushels in lost yield, and the spread of the disease continues to climb. SDS has been documented in almost every state where soybeans are grown. And while growers reported losses often 20–30 percent of a crop, yields can be cut by more than 70 percent.
Daren Mueller, extension plant pathologist and SDS expert at Iowa State University, has witnessed the rapid spread of this disease across the Midwest and has received many questions from Iowa farmers wanting to know what can be done.
SDS field – Daren Mueller
“Growers are interested in maximizing their soybean yields, which involves choosing the right varieties and the right time to plant,” said Mueller. “When it comes to minimizing the impact of SDS, they have to make a tough choice about managing risk – whether to plant early to increase yield potential, or to accept some yield loss associated with later planting to reduce the likelihood of wet conditions conducive to SDS disease development.”
In 2015, Soybean farmers have contended with a number of weather-related challenges leading to a higher probability of SDS. Jason Bond, plant pathologist from Southern Illinois University, notes that with large percentages of the Midwest planted prior to May 20, the risk for SDS rises because of earlier and cooler soil temperatures.
"Abundant rainfall drives higher incidence and severity of SDS. At this point, the only thing that could reduce the impact of SDS is a very dry July and August," says Bond. "Certain seed treatment products bring an additional management option and complement host resistance being deployed."
Bond advises that SDS management start with selecting resistant varieties. Although not immune to the pathogen and disease, SDS symptoms are less severe than with susceptible varieties.
"More than 40 percent of varieties sold have some level of resistance, but not all soybean varieties have been adequately screened for SDS resistance. Bond recommends fields that had problems with SDS in the past should be planted after other fields.
"Stresses like soybean cyst nematode (SCN) have shown interaction with SDS. A good SCN management program increases yield and may help to lessen the impact of SDS," he says.
for more information on how to manage SDS.