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Soybean mosaic (SMV)

© Iowa State University

Pathogen(s) causing disease:

Soybean Mosaic Virus


Appear first on the cotyledons and unifoliate leaves early in the growing season. Angular, red to brown spots that vary in size from tiny specks to 1/4 inch diameter can be seen on the upper and lower leaf surfaces. Leaves with numerous spots rapidly turn yellow and fall to the ground. Spores produced on leaf spots infect the trifoliate leaves, stems, and pods of the soybean plant. Numerous tan lesions, which eventually become dark brown, appear. Later in the season infected leaves may turn yellow and drop prematurely. Defoliation proceeds from the bottom of the plant toward the top of the plant.


Cool, dry conditions which favor vector. Hot weather masks symptoms.


Resistant cultivars, virus-free soybean seed, remove symptomatic plants from seed production fields.



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