By Loren Giesler
Symptoms of sudden death syndrome typically start to appear when soybeans are in the mid- to late-stage pod-filling. This disease is becoming more common in Nebraska, but it still occurs in isolated pockets in many fields. It’s crucial to assess the areas affected and identify the disease correctly to make management decisions for future years.
SDS, which was first identified in Nebraska over 12 years ago, is usually found in small areas of a field. Soil compaction and high fertility levels are associated with increased levels of SDS.
Foliar symptoms of sudden death syndrome start with interveinal necrosis. Spots coalesce to form brown streaks with yellow margins between the leaf veins. Leaves eventually drop, leaving the petiole (leaf stem) attached. The root system will have a deteriorated taproot, and lateral roots will only be evident in the upper soil profile. Plants will typically pull very easily, and a dark blue fungal growth may appear on the roots. (Watch this video).
With any root and stem rot disease it is critical that the stems are split to properly examine symptoms and identify the disease. Brown stem rot will result in the same foliar symptoms as SDS and is also common in Nebraska. In plants with SDS, splitting the stems will show discoloration is confined to the outer stem layers. The center of the stem will not be discolored. The root cortex discoloration will be light gray to brown, and may extend up the stem. In contrast, brown stem rot will discolor the center of the stem with the brown discoloration typically extending from the soil line going up. (Watch this video.)
Accurate diagnosis is critical for proper management for the next soybean crop. If you are uncertain of the cause of damage in your field, have it identified at the University of Nebraska Plant and Pest Diagnostic Clinic. More information on SDS and other soybean diseases can be found in the Soybean Plant Disease Management section of CropWatch.
Giesler is a Nebraska Extension plant pathologist. This report comes from UNL CropWatch.