Sudden Death Syndrome

Every year Sudden Death Syndrome (SDS) can be a potential yield-reducing foliar disease in soybean fields. Though symptoms are generally noticeable mid-to-late in the growing season, infection occurs soon after planting.

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The disease is caused by the soil-borne fungus Fusarium virguliforme, which overwinters in crop residue or soils and can infect soybean plants as soon as one week after crop emergence. It is favored by high-yield environments and is especially prevalent in years when cool soil temperatures occur prior to or during flowering and pod set. SDS is usually most severe in saturated soils, such as in low spots or in areas prone to ponding. Compacted areas such as around field entrances or where machinery has been driven may also exhibit more severe SDS symptoms. In addition, moderate to high populations of soybean cyst nematode (SCN) can be associated with SDS and may increase the severity of SDS.

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Figure 1

Figure 1. SDS Leaf and Stem.

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Temperatures close to 80 °F lead to development of SDS foliar symptoms.1 Foliar symptoms typically occur after the onset of flowering. Initial symptoms of SDS are chlorotic mottling between veins. As the disease progresses, chlorotic leaf tissue turns brown as it dies (Figure 1) and entire leaflets may shrivel in severe cases. Plants will defoliate leaving the petioles attached. Splitting the stem and taproot of a SDS-infected plant will reveal tan to light brown streaks in the cortical tissue while the pith tissue remains white or slightly cream-colored. Root rot or decreased root vigor can be seen in plants with severe foliar symptoms of SDS. If such plants are removed from moist soil, light-blue spore masses of F. virguliforme may be seen. The presence of these spore masses, along with the symptoms mentioned above, is considered diagnostic for SDS.

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Management should include improvements in field drainage, compaction management, use of SCN tolerant or resistant seed products, rotation, later planting in SDS infected fields, and use of Acceleron® Insecticide and Fungicide Seed Treatment Products for soybeans, which can be paired with ILeVO® and Poncho®/VOTiVO®. ILeVO is a seed treatment that provides early-season SDS control (both root rot and foliar phases) and a true nematicide that kills nematodes in the seed zone.