Start scouting for SDS now

Sudden death syndrome usually appears during the last week of July or the first week of August in Iowa, so Iowa State University researchers anticipate symptoms of SDS will begin appearing in the next couple of weeks.

Researchers do not expect SDS to be as widespread or as severe as in 2010. Scientists expect the risk of SDS to be higher in counties with higher-than-normal precipitation.

The first symptoms of SDS are usually found on more compacted and low areas of the field. First symptoms are seen on the leaves of infected plants as scattered, yellow spots between leaf veins. Large sections of leaf tissue between veins turn yellow as spots grow together. These yellow blotches soon turn brown, but the veins remain green. The leaves die and drop, but the petioles remain on the stem.

Infected plants are also easily pulled from the soil because the roots are rotted. When split lengthwise with a knife, the internal tissue of the main or tap root will be gray to reddish brown, not healthy white.

ISU researchers emphasize that, while there are no in-season management options for SDS, scouting is still important for several reasons.

First, this is a good time to evaluate soybean varieties for resistance to SDS. Growing resistant varieties, or avoiding very susceptible varieties, is the most effective way to reduce losses to SDS.

Also, identifying fields or parts of fields with SDS can help with future management practices. These management tactics include reducing soil compaction since the disease has been associated with compacted soil; planting fields with a history of SDS toward the end of a planting schedule when soils may be warmer and drier; and testing for the presence of soybean cyst nematodes.

Soybean cyst nematode is usually, but not always, associated with SDS and may increase its severity, especially in varieties that are SCN-susceptible. Therefore, management practices to reduce SCN populations, including SCN-resistant variety selection and preventing the spread of soil from field to field, may delay onset and spread of SDS.