Charcoal rot is one of the most damaging diseases for soybeans in the South, causing up to 50 percent yield loss in extreme situations. Identification and prevention methods are vital for protection against this stress-induced disease.
Factors to Consider
- Presence of fungal populations
- Weather conditions
- Disease cycle
- Current cropping practices
- Identify the disease. Charcoal rot, also known as summer wilt or dry weather wilt, is an expansive soybean disease developing prominence across the United States. Caused by soil-borne fungus, Macrophomina phaseolina, this disease thrives in hot, dry conditions with temperatures warmer than 85 F. Plant symptoms include empty upper pods, splitting stems and premature yellowing of leaves that eventually brown and die. Most notable is the development of tiny black specks (microsclerotia) just beneath the epidermis of the taproot and lower stem.
- Understand the disease cycle. For identification and precautions, it is important to understand the fungal activity causing this disease. The fungal microsclerotia can survive in the soil for up to two years. The microsclerotia germinate early in the season and infect soybean seedlings through the root system. The fungus develops in the soybean vascular system, interfering with water transport.
- Take preventive steps. There are no known treatments once charcoal rot is found in your fields. If identified, annual rotation out of soybean is needed to reduce future planting risks. Seed treatments, fungicides and tillage have shown no significant control or effect in field studies. Nonirrigated, double-crop soybeans and late planting in the midsouth are at high risk for charcoal rot infestation. Implement stress-reduction methods, such as decreasing plant populations, increasing fertility, controlling competitive pests and supplemental irrigation.
Charcoal rot infections can hurt current and future soybean yields. Understand the disease and take preventive measures to reduce stress in drought conditions and help preserve the field health. For more information, contact your local Mycogen Seeds representative or trusted agronomic adviser.