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Diagnosis is key to future prevention.

Agronomy Bulletin 41 ─ Soybean Sudden Death Syndrome

Situation

Sudden death syndrome (SDS) is one of the most detrimental diseases in soybeans due to limited management options. Correctly diagnosing the disease in the current season can help growers manage its spread in successive seasons.

Factors to Consider

  • Disease symptoms
  • Soil saturation
  • Planting date
  • Planting conditions

Action Plan

  1. Understand SDS. SDS is caused by the soil-borne fungus Fusarium solani f. sp. glycines. The fungus likely infects soybean plant roots one week after emergence, but above-ground symptoms rarely appear before midseason, usually around July. Rains during the crop’s reproductive stage cause the fungus to produce toxins that are then transferred to the leaves, causing the foliar symptoms.
  2. Diagnose SDS. Early symptoms are mottling and mosaic patterns on the leaves. Later, leaf tissue turns yellow and dies. Soon after, the leaflets will die and shrivel. These early symptoms can be signs of other diseases or can mimic chemical burn, so it’s important to examine the inside of the stem and taproot to correctly diagnose SDS. Next, dig up the soybean plant exhibiting symptoms and split the stem in half lengthwise. If the stem is a tan to brown color with the central pith remaining white to cream, the plant is infected with SDS. When SDS-infected plants are freshly dug, a blue mold indicating the presence of the SDS fungus may be found.
  3. Monitor this year's crop. Because the fungus is limited to the root system and fungicides do not transmit to the roots, there is no cure for SDS. Simply observe your fields this year and keep detailed records of any SDS infection.
  4. Plan for next year. Identify fields where you will plant soybeans next year and review the past SDS infestation for each field. Early planting may predispose soybeans to SDS, so plant fields with SDS history last. Soil compaction can lead to poorly drained soils and saturated field conditions during the reproductive stage, which promotes SDS development. Tillage, which can lessen the degree of soil compaction and improve drainage, can help in this regard. Select varieties with a high tolerance to SDS.

Summary

SDS is a fungal disease that has no current treatment. In fields with a history of infection, manage planting dates and soil drainage and plant a variety that shows tolerance to SDS. For more information, contact your local Mycogen Seeds commercial agronomist or trusted agronomic adviser.

Published on Saturday, January 31, 2015