BSR is a soilborne fungus that usually doesn't become actively apparent until August. Optimal temperatures for development are between 59 and 81 degrees F. After the temperature rises above 90 degrees F, the disease is halted. It can be hosted by the soil or infected crop residue. The fungus infects the soybean plant through the root system early on in the growing season, often not appearing until cool, wet weather is followed by hot, dry weather.
Symptoms of BSR are easily confused with that of SDS and are usually worsened by the presence of soybean cyst nematode. The main, easily identifiable symptom is the browning of the pith in the main stem of the soybean plant. The height of the discolored pith is an indicator of the severity of the infection. Less severe cases have browing only at the nodes, while severe cases have continuous discoloration from the base upwards. In certain cases, leaves adopt a brown or yellow discoloration between the leaf veins similar to SDS. The discoloration is followed by curling, wilting, and ultimately death of the leaf. The only true way to tell the difference between BSR and SDS is by looking at the pith discoloration, which is symptomatic only of BSR.