Sudden Death Syndrome Starting to Show up in Soybeans
Sudden Death Syndrome (SDS) symptoms typically start to appear when soybeans are in the mid- to late pod-filling stages. This disease is becoming more common in Nebraska, but still occurs in very isolated pockets in many fields. It’s crucial to assess the areas affected and make sure you identify the disease correctly to make management decisions for future years.
Sudden Death Syndrome, 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.
Sudden Death Symptoms in Soybeans
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 tap-root and lateral roots will only be evident in the upper soil profile. Plants will typically pull very easily and there may be a dark blue fungal growth on the roots. (Video 1)
Split the Stems. 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. (Video 2)
Accurate diagnosis is critical for proper management for the next soybean crop. If you are uncertain of the cause of damage in your field, I encourage you to 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.
On the August 18 Market Journal Loren Giesler talks with host Jeff Wilkerson about what diseases soybean growers should be watching for in the field.
This week Nebraska Extension Plant Pathologist Loren Giesler, whose Twitter handle is @MulletManLG, tweeted out videos from the field showing how to identify sudden death syndrome in soybean (Video 1) as well as how to split and examine the plant stem to differentiate it from brown stem rot (Video 2).