Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00000749
11/12/99
HYDRANGEA DISEASE PROBLEMS - Outdoors
Bacterial wilt may blight the flower clusters and leaves.
The disease is worse after heavy rains and hot weather.
If severe, wilting and root rot occur, followed by plant
death. The causal organism is Pseudomonas solanacearum,
and no chemical control is available.
Bud or flower blight infects dense flower clusters in wet
weather or after frost. The disease is caused by Botrytis
cinerea.
Several genera of fungi cause leaf spots on Hydrangea.
Powdery mildews in different genera cover the undersides
of leaves with light gray mold. The leaves turn brown in
spots and the upper leaf surfaces stay green or turn
purplish brown. Young stems and flower stalks are
infected and killed.
Rust causes rusty brown pustules on the leaves. The
pustules are most noticeable on the undersides of leaves.
Infected leaves dry up and become brittle.
Related information.
Pesticide Recommendations
Powdery Mildew
Fungal and Bacterial Leaf Diseases
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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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