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.