Symptoms of septoria brown spot are small, angular to somewhat circular, red- to brown-colored spots, ranging from minute specks to ¼-inch diameter, on the lower soybean leaves. Individual spots can merge with adjacent lesions to form large, irregular-shaped leaf blotches. Small dark specks may appear on older lesions. The fungus causes infected leaves to turn yellow and drop from the plants. The lifecycle of the septoria brown spot fungus begins when it overwinters in crop residue, infected seed, leaf and stem debris as minute brown fruiting bodies (pycnidia). The microscopic spores produced on living tissues or dead plants are released during wet weather. Wind and rainfall disperses the spores onto healthy plants, and infection begins.
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No soybean variety is completely resistant to brown spot, but varieties differ in partial or rate-reducing resistance and can be used to help protect against the disease. The relative maturity of a soybean variety influences the onset of brown spot. Symptoms appear earlier in the growing season with earlier maturing varieties. Plant high-quality seed within a maturity group to fit your climate, and don’t skimp on seeding rates. Good genetics can add 10 to 12 bushels yield per acre. Choose more than one variety to manage risk and yield potential. Scouting. When scouting soybean fields for weeds and insects, check for the presence of brown spot and other foliar diseases. Begin looking for symptoms on the leaves of young seedlings, especially during the first month after planting. Typically, you will see signs of the disease throughout a field. If you suspect brown spot, take samples and send them to the diagnostic lab recommended by your local county Extension agent, or refer to a pest management guide. Cultural practices. Rotate crops with at least one year between soybean crops. Cultivate crop residues prior to planting to help lower inoculum levels and reduce disease. Disking after harvest is another helpful practice. Plant disease-free seed. Good weed control from preplant, at planting and throughout the growing season also helps protect against diseases and other
Favorable …show more content…
No soybean variety is completely resistant to brown spot, but varieties differ in partial or rate-reducing resistance and can be used to help protect against the disease. The relative maturity of a soybean variety influences the onset of brown spot. Symptoms appear earlier in the growing season with earlier maturing varieties. Plant high-quality seed within a maturity group to fit your climate, and don’t skimp on seeding rates. Good genetics can add 10 to 12 bushels yield per acre. Choose more than one variety to manage risk and yield potential. Scouting. When scouting soybean fields for weeds and insects, check for the presence of brown spot and other foliar diseases. Begin looking for symptoms on the leaves of young seedlings, especially during the first month after planting. Typically, you will see signs of the disease throughout a field. If you suspect brown spot, take samples and send them to the diagnostic lab recommended by your local county Extension agent, or refer to a pest management guide. Cultural practices. Rotate crops with at least one year between soybean crops. Cultivate crop residues prior to planting to help lower inoculum levels and reduce disease. Disking after harvest is another helpful practice. Plant disease-free seed. Good weed control from preplant, at planting and throughout the growing season also helps protect against diseases and other