Field Facts: Septoria Brown Spot
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Septoria brown spot is one of the most common and earliest-emerging soybean leaf diseases. While significant yield loss caused by Septoria brown spot is rare, severe disease pressure can reduce yield by 8%.1
- Common name: Septoria brown spot, soybean brown spot
- Scientific name: Septoria glycines
- Symptoms: Lesions appear as small brown flecks with indefinite margins, typically paired with chlorotic regions. Lesion coloration can range from rusty brown to brown with a purple hue. When lesions enlarge, they merge into irregularly shaped brown areas. Infected leaves can become chlorotic and drop off the plant; this typically happens in the lower to mid canopy.
- Conditions for development: Warm temperatures (60-85 ºF) and humid conditions promote disease development. Extended periods of leaf wetness also are conducive for disease development.
Fast Facts
- The first occurrence of Septoria in the United States was documented in South Carolina in 1923.
- Today, Septoria brown spot is widely distributed across the country and is especially prevalent in agricultural systems in which soybeans are grown continuously.
- Septoria brown spot overwinters on infected soybean residue and spores are released the following growing season when warm, wet conditions are present.
- Septoria brown spot can use weeds such as velvetleaf as an alternate host.
- The potential effect on yield can be estimated by assessing the severity of infection during pod fill, particularly at R6.
Control Tips
- Select soybean varieties with partial resistance to Septoria brown spot.
- Rotating to a non-host crop, such as corn or cotton, can help reduce the inoculum in the field.
- Tillage can effectively bury crop debris and cause a rapid decay of the fungus.
- Apply foliar fungicides from R3-R5 to reduce spread of the disease during pod fill.
- Corteva Agriscience offers Aproach® Prima fungicide to protect against Septoria brown spot and other key soybean diseases.
- Aproach Prima should be applied prior to disease development for best results. Work with your Corteva Agriscience representative to determine the optimal timing for soybean fungicide applications.
1 Septoria brown spot. University of Minnesota Extension. https://extension.umn.edu/soybean-pest-management/septoria-brown-spot
Aproach® Prima is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.