Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001281
11/12/99
ROSE DISEASE PROBLEMS
Bacterial leaf spot causes dark brown sunken spots on
the leaf and flower stalks. The flower buds die without
opening. The disease is worse in spring. Cut out and
destroy infected plant parts.
Crown gall causes formation of roundish galls (Vis. 5) with
irregular rough surfaces. Galls above ground level should
be pruned off and destroyed. Galls on the plant crown are
not easily pruned off so destroy the whole plant. Avoid
infested soil.
Rose anthracnose causes purplish brown, circular, one-half
inch leaf spots. The center of the spot turns gray and
drops out. Black spot sprays generally control this
disease.
Black spot causes black spots (Vis. 1) on the leaves. The
leaves turn yellow (Vis. 2) and drop. Remove and destroy
fallen infected leaves.
Botrytis blight causes flower buds to turn brown and
decay. The petals of unopened flower buds (Vis. 3) are
easily lifted off the stem. Infected blooms may eventually
be covered by a gray mold (Vis. 4). Remove old flowers as
they fade.
Powdery mildew causes upward curling of young leaves
and makes a white, powdery coating (Vis. 6) on the leaves.
Brand canker develops while plants are under winter
protection. Infected roses have a black sooty appearance
when uncovered in the spring. This disease is sporadic
and does not directly affect the blossoms or leaves.
Destroy infected canes.
Brown canker causes cankers with light chestnut brown
centers and deep purple margins. Small flecks and purple
spots form on the leaves. This disease attacks canes
while the roses are under winter protection. Brown canker
may be worse on bushes hilled with soil.
Common stem canker gains entrance through a wound.
Young cankers are pale yellowish or reddish, becoming
brown, sunken and cracked. Destroy cankered canes. Black
spot sprays usually prevent new infections.
Dieback, cane blight canker causes leaves on the cane
above the canker to wilt, turn brown and die. Destroy the
cankered canes. Sprays for black spot may prevent new
infections.
Rust causes orange colored spots on the leaves and stems.
Clean up infected leaves at the end of the season.
Related information.
Pesticide Recommendations
Black Spot
Cankers
Powdery Mildew
Fungal and Bacterial Leaf Diseases
Botrytis Blight
Bacterial Crown Gall
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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.
For more information about this data base or its contents please contact
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