As we advance into mid-August, late summer soybean diseases are now showing above the soybean canopy.

Many of you have been bringing in plant samples or have called me to walk your fields with you to diagnose dying areas within fields.

Sclerotinia stem rot (White Mold), early season sudden-death-syndrome and brown stem rot are all making early appearances throughout Ohio. OSU Extension Soybean pathologist, Dr. Anne Dorrance reminds us that late season diseases — those that typically occur when soybeans reach the growth stage in which the seed is 1/8-inch long in pods at one of the top four nodes of the plant — are making some early appearances this year due to the substantial rains and cool weather conditions in the state.

White mold looks like a fluffy white growth which is also called mycelium and can be seen on the stems. Soon, affected plants will die. This fungus survives in soil as hard black bodies which look like rat droppings except they are pink on the inside. Management consists of planting resistant varieties, seed treatments and using lower seed populations at planting.

Sudden death syndrome and brown stem rot are similar in foliar diagnostics, yet very different. There are some early foliar symptoms showing up on isolated plants in some fields. Yellow, irregular shaped to circular spots are forming between the veins and these are already turning necrotic or browning. One key factor that separates these two diseases is the color of the pith – for brown stem rot, the pith (center of the stem) turns a chocolaty colored brown while for sudden death syndrome it remains white, but the internal tissues of the tap root are gray colored.

SDS usually shows in areas of high equipment traffic that results in compaction and poor drainage or areas that are affected by soybean cyst nematode.

For more information and pictures on these issues, please see my blog under “Clark County Agronomic Crop Update,” dated Aug. 11, 2009 at http://westohcropweather.blogspot.com/.

Jonah T. Johnson is an educator with the Ohio State University agriculture extension office for Clark County.