There were multiple reports of Sudden Death Syndrome (SDS) in soybeans this past year. The cooler, wet season helped promote the disease in susceptible varieties, but the presence of soybean cyst nematode (SCN) can also increase the effect of SDS.
The combination of the fungus that causes SDS (Fusarium solani f. sp. glycines) and SCN will have a greater effect on yield on a variety that is susceptible to both pathogens than either pathogen would on its own. Both pathogens are present in Tennessee, so I recommend sampling for SCN. The best time to sample for SCN is in the fall (now), when the population is the highest. More information on how to sample for SCN and mailing instructions can be found at UTcrops.com (Nematode Sample How To and Nematode Sampling Form). There is no charge for processing of SCN samples.
More information on SDS can be found in the article posted earlier this year at news.utcrops.com (Sudden Death Syndrome in Soybeans). One management option is to plant a resistant to moderately resistant variety. Disease ratings on soybean varieties can be found at UTcrops.com within the UT Variety Trial Data and Soybean Disease Rating Summaries (2013 variety trial data will be available by the end of the year which will have information on SDS resistance/tolerance).