Anne E. Dorrance
Patrick E. Lipps
Dennis R. Mills
Brown spot is also known as Septoria leaf spot. Its primary effect is premature defoliation of soybeans, but some yield loss may occur during extremely wet growing seasons. Rarely in Ohio has brown spot caused economic yield reductions. The primary effect has been early defoliation of lower leaves.
Septoria brown spot. |
Brown spot of soybeans is caused by the fungus, Septoria glycines which overwinters in infected soybean straw. During moist weather, spores are produced on crop residue and disseminated by wind and rain to nearby soybean plants where soybean leaves are infected. Fruiting bodies develop in lesions on infected cotyledons and unifoliate leaves. Spores, which develop in these fruiting bodies, provide inoculum for later infections of trifoliate leaves, stems, and pods as well as neighboring plants.
High moisture and moderate temperatures (60°85°F) favor infection and disease development. Spread of the fungus is usually halted during hot, dry weather.
Additional information is available from your local Extension office or The Ohio State University Plant Pathology website (www.oardc.ohio-state.edu/ohiofieldcropdisease).
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868