Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001025
11/12/99
PAEONIA DISEASE PROBLEMS
Botrytis blight causes leafy shoots to wilt suddenly and
fall over. The stem is covered with gray mold just above
the soil. Spores are carried to young leaves and flower
buds causing leaf blight and bud rot. The leaf blight stage
occurs sometime after flowering. Recently opened flowers
are also attacked. All infected parts turn brown and are
later covered with gray mold. Cut and remove old growth.
Do not plant peonies in basins that collect water. Do not
heap soil around the base of plants.
Downy mildew causes entire shoots to blacken and die.
Cankers form on the stem causing them to fall over. The
crown may rot. Infected plants should be destroyed.
Leaf spots may be a problem. Destroy plant residues in
the fall.
Peony leaf blotch is also known as red spot or measles.
Small circular discolored leaf spots run together causing
irregular blotches. The upper surface becomes dark
purple, the lower surface light brown. On young stems the
spots appear as reddish brown streaks. All parts of the
plant may be spotted. Remove diseased residues at the end
of the season.
Crown gall causes the formation of rounded, rough galls.
The galls are usually found at the soil line. Destroy
infected plants and avoid infested soil.
Anthracnose causes sunken stem lesions. The lesions may
girdle and kill the stalk.
Stem rot is worse in humid summers. The stalks are killed
and a cottony mold form on the stems. Remove and destroy
infected plants and plant parts. The disease is caused by
Sclerotinia sclerotiorum.
Verticillium wilt causes plants to decline and die. Remove
infected plants and avoid infested soil.
Bud Blast is a noninfectious problem. The flower buds
reach the size of a pea and fail to open. The problem is
associated with lack of potassium, dry weather, low
temperatures in early spring, excessive shade, deep
planting and infertile soil.
Oedema is caused by excessive atmospheric and soil
moisture. Numerous small brown or purple spots develop
on all parts on the plant above ground. This problem is
usually not serious.
Related information.
Pesticide Recommendations
Botrytis Blight
Fungal and Bacterial Leaf Diseases
Verticillium Wilt
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.
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