While 2011 was relatively quiet for Sudden Death Syndrome, it was not that way in 2010 hitting large areas of Iowa and parts of Illinois. This put it back on the radar as far as things to watch for.
What is Sudden Death Syndrome? Sudden Death is caused by a soil-borne fungus, Fusarium Virguliforme. This can infect soybeans usually when conditions are cool prior to towering. High soil moisture can also increase odds of plants contracting the disease. High Cyst Nematode feeding will also increase the chance of infection by giving the fungus paths into the plant through weakened tissue the cyst has created with its feeding.
What should you look for? To me the big telltale is the leaf damage. Damage starts out as yellow spotting on the upper leaves. As the disease progresses, the leaves will take on a more tiger-stripped appearance with green veins, and a yellow and brown tissue between the veins. The leaf damage will progress from the top leaves down to the base leaves. Leaf damage may look a little like Brown Stem Rot, but the stem of the plant should be split open and the center (pith) of the stem should be checked. In Sudden Death the pith remains white, while in Brown Stem Rot the pith is brown. If soil is moist and you can pull the roots up without too much disruption, you can occasionally see a purple fungus on portions of the root. Infection sites tend to be small patches in the field, which are usually lower spots prone to water saturation or compaction.
What do you do about Sudden Death? Sudden Death Syndrome in our sales area is only a very rare event. I would not change much in my program unless Sudden Death is a yearly occurrence. At this time, fungicide application is not an option. This leaves variety selection as your main control to combat Sudden Death. Varieties are screened for tolerance to Sudden Death. Picking one that has high tolerance along with high Cyst protection should go a long way in keeping Sudden Death as a non-issue. Fixing drainage issues and compaction in your fields also will help.