Scattered showers and rain favor development of a disease of soybean known as brown spot, caused by the fungus Septoria glycines . The fungus survives from season to season in crop debris and seed.
Spots occur most prominently on lower leaves of plants.
Infected leaves gradually turn yellow and drop off the plant. However, when the environment is favorable for disease development late in the season, fungicides may be used to prevent premature defoliation. This, however, requires that two fungicide applications be made and this is usually not economical. The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.