As if yield losses to dry weather stress weren’t enough, the drought of 2012 has brought another problem to the forefront of soybean producers in the Upper Midwest – Charcoal Rot. Also known as dry weather wilt, this is a soil-borne root and stem disease that usually develops in mid-to-late summer when plants are under severe heat and drought stress. Not since 2003 has there been an outbreak of this disease that had a major impact on yields and the effect on this year’s crop could be the worst in recent memory.
Spores overwinter in plant tissue and can survive for several years in dry soil. Infected plants often appear yellow, wilted and stunted. These symptoms are very similar to other yield-robbing problems that farmers experience in our growing region, so they may go unnoticed or could be attributed to other pests like Soybean Cyst Nematode (SCN), Brown Stem Rot, Sudden Death Syndrome or even Iron Chlorosis. One fairly easy method of identification is to dig up soybean roots and take a knife to gently scrape off the epidermis (outer layer) of the root. Gray-colored lines or striations present throughout the root tissue are an indication of Charcoal Rot.
There are no viable methods to manage this disease other than to do your best to insure ample moisture for your crop throughout the growing season. Anything that reduces soil moisture, including unnecessary tillage passes or excessive tillage, will add to the impact of the disease. There is no known varietal resistance available on the market today, however, there are some soybean cultivars that show tolerance to Charcoal Rot. Contact me or your local Latham® representative for more information.