Onion smut has become a serious problem for direct-seeded onion in many areas. Symptoms appear on cotyledons and young leaves as longitudinal blisters that are blackish with a silver sheen. Dark pustules (sori) appear as slightly thickened areas at the base of seedlings near ground level. Blisters rupture to expose black, powdery spore masses (smut teliospores). Affected leaves may bend or twist abnormally and usually are shed prematurely. Elongated, raised black blisters can also be found in the outer scales of the developing bulb. Affected plants are usually severely stunted. Apart from onion, other members of the onion family including wild Allium spp., leek, and shallot are also attacked.
R. K. Sampangi and S. K. MohanParma R & E Center, University of Idaho, Parma, ID 83660Email: Sampangi@uidaho.edu
APS publication number: IW000113
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