Sudden Death Syndrome

By Berlin Nelson, Professor, Dept. Plant Pathology

Sudden death syndrome (SDS) has not been reported in North Dakota or northern Minnesota but may appear in the near future. It is reported in northern Iowa. The disease is caused by specific strains of Fusarium solani that differ from the strains that cause Fusarium root rot. Yield losses from SDS can be severe when symptoms occur early during flowering.

The symptoms of SDS generally begin on the leaves at or just after flowering. Symptoms are scattered circular to irregular shaped yellow spots, at first interveinal, that produce a mottled appearance to the leaves. Eventually the yellow tissue dies and green tissue remains only along the major leaf veins. The upper leaves are the first to defoliate; complete defoliation can occur when disease is severe. Flower and pod abortion occurs. Plants showing severe leaf symptoms also will have extensive decay of roots and plants are easily pulled from the soil. Diseased plants or groups of diseased plants are typically scattered in the field. Disease development is associated with wet, cool conditions early in the growth of soybean plants, but with warmer temperatures during and after flowering. SDS appears to be more severe in non-tilled than tilled soybeans. SDS foliar symptoms can be similar to those caused by brown stem rot.

Management

There are differences in cultivar susceptibility to SDS, but highly resistant cultivars adapted for North Dakota and northern Minnesota have not yet been identified. If the soybean cyst nematode is present in fields with SDS, control of the nematode will help reduce SDS severity. There is some evidence that crop rotation will reduce populations of the SDS fungus in the soil. Dry beans, however, may be a host of the SDS strains of F. solani. Because SDS is favored by excess soil moisture, practices that encourage drainage will help minimize disease development. Reducing soil compaction can reduce severity of SDS.

For further information visit this North Central Soybean Research site: