Plant Health Initiative

Sudden Death Syndrome - Management

SDS field trials in Illinois. A side-by-side comparison of a SDS-resistant variety (DX=10) on the left and a susceptible variety (DX=89) on the right. Photo credit: Cathy Schmidt, Southern Illinois University

Effective management of SDS requires an integrated approach:

• Plant SDS-resistant varieties. If SDS is causing defoliation in your field, do not plant highly susceptible varieties. Ask your seed dealer for information on varieties with partial resistance or tolerance to SDS.
  
  Another source of information is the Southern Illinois University SDS program, which tests nearly 900 commercial soybean varieties (MG 1 to V) each year for their reaction to SDS. Scores are taken as close to growth stage R6 (full seed) as possible. Note that the SDS Disease Index (DX) value has a range of 0-100. Read the 2008 results (in pdf format) »
  
  Yield data is not included in the tests, but in general, for every DX increase of 10 units, there is a 7% decrease of potential yield.
• The presence of SDS usually means that the soybean cyst nematode (SCN) is also present, and the presence of SCN can alter the reaction of a soybean variety to the SDS pathogen.
  
  It's a good idea to plant a soybean variety with SCN resistance to manage this pathogen and limit yield loss. Most seed companies have data on SCN resistance for their varieties.

• Plant in warmer soils. The pathogen prefers cool soil for infection. Move planting dates a week or two after regular early planting dates or till to promote earlier warming of soils. Maintain crop fertility based on soil tests.
• Reduce SCN populations. The fungus can overwinter in cysts of the soybean cyst nematode (SCN), thus increasing its survival ability from season to season. Thus, the presence of SCN may favor development of SDS. Management practices to reduce soybean cyst nematode populations are thought to also delay onset of SDS.
• Practice crop rotation. A two-year rotation between soybean crops and maintaining good crop nutrition have been shown to reduce incidence and severity of SDS.
• Harvest corn fields cleanly. X.B. Yang reported in Manage Soybean Diseases at Harvest Time (Crop News, September 2009), that the management of SDS for future soybean fields should start when you harvest corn fields. His group compared the survival of SDS fungus in different crop residues (corn or soybean) which included different parts of a crop (root, seed, straw), and found that corn kernels consistently had the highest SDS fungus population. This corresponded with observations that severe outbreaks of SDS can occur after a few years of continued corn production. A nice and clean harvest of corn field should help reduce the risk of SDS, while a high amount of harvest loss increases SDS risk the next time soybean is planted.