What to Consider
Sudden death syndrome is caused by the soil borne fungus, Fusarium virguliforme. Symptoms appear after flowering and during pod fill and include -
- initially, small yellow spots on upper leaves,
- chlorosis expands interveinally along with necrosis (Figure 1),
- pith tissue remains white and internal root tissue is discolored,
- green vein pattern remains on leaves until defoliation (Figure 2),
- increased flower and pod abortion,
- reduced seed size and quality.
Symptoms can resemble those of other diseases, such as southern stem canker.1 However, leaves and pods affected with SDS drop from plants as opposed to remaining on plants as with southern stem canker.1 Unlike soybean plants infected by brown stem rot, an SDS-infected plant should have a white, decay-free pith (Figure 3). Although the pith remains white, discoloration of the stem occurs as the vascular tissue deteriorates along with the lateral roots and root nodules. Sudden death syndrome can affect entire fields but usually begins as scattered areas within fields. Unfortunately, if SDS symptoms appear, there is no treatment for the current crop.
Yield losses from SDS can range from slight to nearly 100% and are dependent on disease onset and severity.1 The fungus overwinters in crop residue or soils and can infect soybean plants soon after planting.2 Sudden death syndrome is usually most severe in saturated soils.3 Soils with major compacted areas such as field entrances may also exhibit more severe SDS symptoms. Moderate to high populations of soybean cyst nematode (SCN) can be associated with SDS and may increase the severity of the disease.2,3
Management should begin before planting to help reduce infection in fields with a history of SDS. Foliar fungicides are not an option for SDS control due to the nature of the disease.4 An integrated management plan for SDS may include the following:
- Plant soybeans with good disease packages. Soybeans with good to excellent rating for tolerance to SDS and also those that are described as resistant or moderately resistant to SCN should be chosen.4 Consult your seed guide for SDS and SCN tolerance ratings.
- Delay planting or plant earlier maturing products to possibly help soybean plants escape SDS infection. Cool, wet soils promote infection.
- Cultural practices to improve water drainage, reduce SCN population or alleviate soil compaction layers may lessen SDS severity.
1 Faske, T., Kirkpatrick, T., Zhou, J., and Tzanetakis, I. 2014. Soybean diseases. Arkansas Soybean Production Handbook. University of Arkansas.
2 Westphal, A., Abney, T.S., Xing, L., and Shaner, G.E. 2008. Sudden death syndrome of soybean. The Plant Health Instructor. https://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/SuddenDeath.aspx
3 Malvick, D. 2010. Sudden death syndrome of soybean: favorable conditions and request for samples. University of Minnesota Extension.
4 Bradley, C. 2014. Destructive diseases of soybean—sudden death syndrome and white mold—observed in the state. The Bulletin. The University of Illinois.
5 4-Year Average Yield Protection Advantage over control, across all locations and thresholds, N=341Trials (2014, 2015, 2016, 2017) (AR, GA, IA, IL, IN, KS, KY, LA, MD, MI, MN, MO, MS, NC, ND, NE, OH, SC, SD, TN, TX, VA, WI). Results will vary based on nematode pressure in each field. http://www.acceleronsas.com/Pages/NemaStrikeTechnology.aspx
Web sources verified 8/2/2018