Submitted to: The Plant Health Instructor
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/7/2007
Publication Date: 1/8/2008
Citation: Westphal, A., Abney, T.S., Xing, L., Shaner, G. 2008. Sudden Death Syndrome. The Plant Health Instructor. Available at: http://apsnet.org/education/LessonsPlantPath/SuddenDeathSyn/default.htm. Interpretive Summary: Soybean yield losses due to sudden death syndrome (SDS) occur regularly. This increasingly important disease is caused by a toxin producing form of the Fusarium fungus that has become a serious root rot disease of soybeans in almost all production areas. Abundant moisture during the early reproductive stages of the host enhances SDS damage. Root infections are common and occur early, but seldom advance into the taproot prior to the flowering stage. Delayed planting and management practices that improve plant health during the flowering period help reduce disease losses. Results of studies on yield loss and foliar symptoms with diverse soybean germplasm sources indicate the disease can be very destructive. Most soybeans tested to date are somewhat susceptible to the disease. While most seed companies have removed highly susceptible cultivars from their inventories, no highly resistant cultivars are available. Only a few soybean varieties derived from a narrow genetic base have been identified as having some degree of resistance. Equally important, variety reaction to SDS appears to be conditioned to some degree by the soybean cyst nematode (SCN), tillage practice and crop rotation. Awareness of this information will permit researchers and producers to recommend and employ control strategies that can minimize important yield losses caused by SDS.
Technical Abstract: Sudden death syndrome (SDS) is an important disease of soybean in North and South America. SDS first occurred in South America in the early 1990s. In the U.S.A., SDS was first detected in AK in 1971. Now SDS occurs in most soybean production areas of the U.S. The SDS pathogen is a soil-borne fungus and within clade 2 of the Fusarium solani species complex. In North America, Fusarium virguliforme (= Fusarium solani f. sp. glycines), is the causal agent. In South America, F. brasiliense, F. cuneirostrum, F. tucumaniae, and F. virguliforme cause SDS symptoms. The fungus may infect roots of soybean seedlings soon after planting, but foliage symptoms of SDS rarely appear until plants are flowering. Toxins produced by the fungus in root tissue are translocated to the leaves causing symptoms that lead to premature dying. The extent of yield losses depends on the severity and timing of disease expression. SDS is most severe when soybean is planted early into cool, wet soils, when heavy midsummer rains saturate the soil, and when the soybean cyst nematode (SCN) is present. It is important to select cultivars with a known history of SDS resistance. Only a few soybean varieties derived from a narrow genetic base have been identified as having moderate resistance. Utilization of additional management practices that improve plant health such as cultivar resistance to SCN, planting date, tillage practice and crop rotation that appear to condition SDS severity are also important in reducing SDS yield losses. Information presented in this manuscript will permit researchers and producers to recommend and employ control strategies that can minimize important yield losses caused by SDS.