September 09, 2004

Yield loss from soybean SDS could reach $100 million

by K.C. Jaehnig

Soybean sudden death syndrome, or SDS, hit a record number of fields in Southern Illinois this year but didn't pack as much of a wallop as feared.

"We rate severity on a scale of one to four, with one being a few sporadic plants and four being more than 60 percent of a field badly affected. In 2000, we saw a lot of fields with fours, but this year I never saw anything higher than a three, and for the most part, counties averaged between a one and a two.""It was the worst year since 2000 in terms of prevalence, but overall the severity was much lower," said Southern Illinois University Carbondale plant pathologist Jason P. Bond.

Even so, SDS remains a major contender when it comes to knocking out yields.

"Extrapolating from what we saw in Southern Illinois, I'd guess that yield loss from SDS could come to at least $100 million this year, and this was just in the fields we drove by," Bond said.

"I think there are probably a lot of farmers who got hurt pretty bad that we didn't see."

As part of an annual "windshield survey," Bond and SIUC soybean expert Oval Myers spent the last week in August checking out bean fields in every county in the lower half of the state.

Clark, Coles, Jasper and White counties got the worst of it this year, with SDS in more than 80 percent of the fields surveyed.Colleagues from the University of Illinois did the same for the upper half. The 5,000-mile look-see, first funded by the Illinois Soybean Checkoff Board in 1999, gets its name from the fact that most of it takes place from behind the wheel.

"These four counties had their highest incidence ever - - in White County, 92 percent of the fields we looked at had SDS," Bond said.

"White, Jasper, Coles, Wabash, Edwards and Randolph counties also experienced high severity, where Clark only scored a one."

Before the survey, researchers were bracing for a hard-hitting disease year because conditions so closely mimicked those in 2000.

"We had the rainfall, the cold temperatures, the early planting, the cool fronts throughout the season at the critical growth stages, we even had SDS showing up in some fields just a few weeks after planting - - the first time that's ever been documented here," Bond said.

So what kept the crop off the ropes? More farmers planted SDS-resistant varieties.

"We might have had a similar year (to 2000 in terms of severity) if it hadn't been for that shift," said SIUC soybean breeder Michael E. Schmidt.

"In our variety testing program, we use known susceptible varieties as a way of monitoring the disease across time. This year, those varieties were hit almost as severely as they were in 2000."

While SDS is not yet down for the count, the growing number of resistant varieties does mean it's lost some of its punch.

"There are about four times as many varieties that fall in the moderately resistant to resistant categories than there were in 2000," Schmidt said.

"We still have work to do because susceptible varieties are still in the marketplace, but farmers are in a much better position to choose than they were a few years ago."

With so much to choose from, selecting the right resistant variety might seem a little dicey, but in many cases, help is only a mouse click away.

The SIUC team has just finished evaluating the SDS resistance of more than 1,000 commercial varieties; results appear on the University's Web site at

Farmers also can check out VIPS (Varietal Information Program for Soybeans), run by the University of Illinois extension office.