According to Ohio State University soybean experts Anne Dorrance and Pat Lipps, SDS is a fungal disease of the Fusarium variety. “Symptoms of SDS begin as small, bright, pale green to yellow circular spots on the leaves,” the researchers point out. “As the disease progresses, brown to tan areas surrounded by chlorotic tissue develop in between the veins. More importantly, soybean plants with SDS also have substantial amounts of root decay and discoloration of roots and crown.” When scouting fields for the disease last week, I observed varying stages of disease development, from early display of those symptomatic circular lesions, to fields where significant acreage displayed the characteristic brown tint of more developed SDS.

So what causes this disease? The fungus lives in the soil, meaning once a field is infected, a producer will be managing the disease for quite some time. Dorrance and Lipps tell us that some growing seasons will present higher levels of SDS thanks to Mother Nature. “Some of the factors that favor disease development include high soil moisture during the vegetative growth period and unseasonably cool temperatures prior to or during flowering and pod set.” Gee, do those conditions sound familiar to anyone this year?

Agronomy Research Scientist Jim Trybom at Pioneer Hi-Bred International says SDS is a fairly troublesome disease often ranked second only to soybean cyst nematode (SCN) in causing decreased yields and economic loss.

“Because SDS is more weather-related, its impact and reach can vary year to year and area to area,” says Jean Liu, Pioneer research scientist, soybean pathology. “This year in April, many areas had warm conditions, then two or three weeks of cooler weather in May. Growers who planted soybeans shortly before or during the period of cool, moist conditions (i.e., from late April to mid-May) need to pay attention, because SDS fungus can infect roots as early as seedling emergence. Early infection would aggregate the problem and cause greater yield reduction compared to late infection.”

If you’ve observed SDS in your field, there isn’t a lot you can do about it … this growing season. The importance of scouting for SDS now is in doing effective preventative maintenance next growing season. “Growers must clearly understand the extent of infection in each of their fields to effectively manage SDS,” Pioneer’s Trybom says. “If SDS is identified, growers need to maintain the field history and select varieties with higher tolerance to SDS in the future. Variety selection and good field drainage are some of the best tools available to counter most disease threats.”

In addition, Trybom recommends growers focus on planting the most problematic fields last, managing Soybean Cyst Nematode (SCN), improving field drainage, reducing compaction, evaluating tillage systems and reducing other stresses on the crop. The Ohio State researchers agree, listing resistant variety selection as the top management tool for SDS. They also recommend examining your crop rotation practices, considering a rotation that only puts soybeans in an affected field once every three years.

SDS isn’t the end of the soybean production world. Some seasons, like this one, it will be worse than others.

Companies like Pioneer and Monsanto are diligently developing more traits to help farmers manage the disease, and seed companies across the country offer more resistant varieties each season. Scout your fields early and often, and good luck this harvest.