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Protect your flock.
Septoria Brown Spot in Soybean
October 2025 |听Written by:听Madeline Henrickson and Dr. Alyssa K. Betts
Pest Background
- One of the most common foliar diseases of soybeans.
- Caused by the fungus Septoria glycines.
- Present in most fields at some level every year.
- Disease is favored by high rainfall and canopy moisture.
- Hot, dry conditions will keep symptoms in the lower canopy.
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Identification
- Symptoms begin as small brown spots that can have a yellow halo around them, as spots coalesce the leaf may turn yellow (Figs 1 and 3).
- Infected leaves may drop prematurely (Fig 2).
- If symptoms remain in the lower canopy, yield is not usually impacted.
Fig 1: Septoria brown spot in the lower canopy. Photo by Dr. Alyssa Betts
Fig 2: Leaf drop due to upper canopy infection
Fig 3: Early symptoms of septoria brown spot
Management
- The pathogen overwinters on infected leaf and stem debris.
- Rotation to non-host crops like corn and small grains can reduce pathogen survival.
- Susceptibility varies across soybean varieties, but since there are no known sources of resistance, ratings for this disease are not often provided.
- If disease is rapidly moving up the canopy, fungicides can be applied according to the label at the R3 to R5 growth stages to slow disease spread into the middle
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References
Crop Protection Network (2022, Jan 25).
Septoria Brown Spot of Soybean. Retrieved听from:
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Authors:听Madeline Henrickson and Dr. Alyssa Betts
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