Scouting for disease: White smut

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.    

Hosts: Aster,  Echinacea, Gaillardia, Helianthus and Rudbeckia.

Symptoms
: Round, white spots, up to one centimeter in diameter. Young lesions may create very faint spots. Over time, the spots turn brown and become necrotic.

Spread
: Spores are formed inside the leaf tissue. As lesions mature, the leaf surface ruptures releasing the spores. Spores are wind-dispersed. A white, powdery material may be visible on the leaf surface. Spores of this fungus are not known to survive winters in the northern United States.

Management
: Remove all symptomatic plants. Plants in greenhouses may need fungicide applications for good disease control. The disease is favored by cool, humid conditions; disease spread will be slow under warm, dry conditions.

Note
: Of the hosts listed, Gaillardia is most susceptible. The disease has been documented on the cultivars ‘Goblin’, ‘Baby Cole’ and ‘Fanfare.’ This disease has been seen with increasing frequency in the past few years.

Gaillardia foliage
Whitish, round lesions on Gaillardia foliage.
Photo credit: D. Brown-Rytlewski, MSU.

gaillardia necrosis
Older lesions caused by white smut on
Gaillardia have coalesced and are causing
necrosis.

dieback
Dieback caused by a severe white smut
investation on a landscape planting of
Gaillardia.
Photo credit: D. Brown-Rytlewski, MSU.

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