Sudden death syndrome (SDS) is here and has been reported in several areas of the state where rainfall has been plentiful. This year Mike Roegge has also seen SDS in isolated areas where beans were planted early in Adams County, despite recent dry conditions. With the weather we've had this season, we suspect this year could be a good one for development of SDS. Symptoms produced by SDS begin as chlorosis and necrosis of the interveinal tissue of soybean leaves, which eventually coalesce and form large yellow and brown areas between the green midvein and green lateral veins. Infected plants in the field prematurely turn yellow and then brown, whereas healthy plants remain green. More information on SDS can be found in issue no. 17 of the Bulletin.
When diagnosing SDS, do not rely entirely on foliar symptoms. Remember that the foliar symptoms of SDS are similar to those of brown stem rot and stem canker. Longitudinally split the stem of plants exhibiting foliar symptoms and look for stem discoloration. Plants with SDS may have some uniform vascular discoloration (reddish to brown), but the pith remains white. Plants with brown stem rot have brown discoloration of the vascular tissue and the central pith. Leaf symptoms of the stem canker disease can also be confused with SDS; however, soybeans with stem canker have cankers on the lower stem, whereas plants with SDS do not have cankers. The leaves remain attached after dying on plants that have stem canker; but, on soybeans with SDS, the leaves drop off the soybean plant, often dropping from the top of the plant first and leaving the petiole attached to the stem.--Loretta Ortiz-Ribbing