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Sudden Death Syndrome Increasing in South Dakota Soybeans

Sudden Death Syndrome Increasing in South Dakota Soybeans

Planting resistant varieties, selecting well drained fields and managing soybean cyst nematodes can help control the disease

SDSU Extension plant pathologists say they saw a rise in Sudden death Syndrome in soybeans in South Dakota this year.

"The heavy rains following planting in early June combined with late season rain have provided ideal conditions for the disease to develop," say Emmanuel Byamukama and Febina Mathew, SDSU Extension plant pathologists.

In a survey of 209 soybean fields covering 24 counties in South Dakota (Union, Clay, Yankton, Lincoln, Turner, Codington, Clark, Spink, Brown, Marshall, Roberts, Kingsbury, Miner, Sanborn, Davison, Hanson, McCook, Minnehaha, Lake, Deuel, Hamlin, Brookings, Grant, and Moody), found visual symptoms of SDS in 30 fields in 18 counties.

Initial leaf symptoms of sudden death syndrome. Note the light green to yellow spots on the leaves caused by sudden death syndrome pathogen. Photo: Emmanuel Byamukama, SDSU

In 2013, SDS was confirmed in eight counties.

Only four counties (Lake, Brown, Brookings and Yankton) were positive for SDS in both 2013 and 2014.

However, yield losses were expected to be small. Only a few of the more infected soybean fields will have low to moderate yield losses from SDS.

Like other root rots, SDS often appears first in patches in the field, such as low, poorly drained or compacted areas, says

The disease incidence can pick up when soybeans are exposed to cool, moist soil conditions early in the growing season. Although SDS affects soybean plants during the vegetative stages, symptoms usually do not appear until the reproductive stages of crop development. SDS begins as small, bright, pale green to yellow circular spots on the top leaves during flowering or pod-fill. As the disease progresses, the tissue in these spots starts to die and enlarges to form dark brown spots between the veins

SDS is often, but not always, associated with high levels of soybean cyst nematode (SCN) infestation. The SDS fungus can also use the protective environment inside SCN cysts to survive the winter. Thus, it is important to continue to make SCN sampling and management a priority.

SDS management can be accomplished through an integrated approach: use of resistant cultivars, planting in well drained warm soils, crop rotation, managing SCN, and harvesting corn cleanly (SDS pathogen can survive on corn kernels). Foliar applied fungicides are not effective against SDS.

Source: SDSU Extension

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