Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00000489
11/12/99
DAHLIA DISEASE PROBLEMS
Crown gall causes large abnormal growths at the base of
the infected plant. The plants are stunted and the shoots
spindly. Infected plants are destroyed.
Bacterial wilt causes stem drooping and wilting. Infected
stems have a wet soft rot near the soil. Destroy infected
plants and rotate plantings.
Bacteriosis causes browning and softening of the stem.
The pith is moist and blackened with the rot extending
into the bark. A foul odor is associated with the
disease. The roots may be infected.
Botrytis blight is worse in dull cloudy weather. The buds
rot and infected parts may be covered with grayish powdery
mold. Remove infected plant parts.
Powdery mildew causes white or grayish mold. The disease
is worse late in the season and badly infected leaves are
distorted and drop.
Verticillium wilt causes brown or black streaking in the
conductive tissue of the stem. Plants wilt and die.
Stored roots rot if infected. Destroy infected plants and
rotate plantings.
Dahlias growing in heavy wet soil, and infected with stem
rot, wilt and die. A white mold encircles the stem at the
soil line. Improve soil drainage and do not crowd the
plants. Rotate plantings.
Dahlia mosaic virus causes leaf mottling. Pale green
bands develop along the midribs and leaves are dwarfed and
show general mosaic or yellow spotting. Destroy infected
plants and control the aphids that spread the disease.
Related information.
Pesticide Recommendations
Bacterial Crown Gall
Botrytis Blight
Viral Leaf Diseases
Verticillium Wilt
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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