Question: Why do peony leaves and foliage develop
spots and blotches and then die by late summer?
Answer: There are several peony leaf diseases
which can cause foliage symptoms and death. The most common of
these is Botrytis blight (gray mold) caused by the fungus Botrytis
This fungus can infect shoots, stems, leaves, and flowers anytime
during moist periods in spring and summer, causing infected parts
to turn brown and die. Another disease, caused by the fungus Cladosporium
paeoniae, causes small red spots which can coalesce to form
irregular purple blotches on leaves and stems. Red spot can lead
to deterioration of peony foliage by late summer as can several
other leaf spots caused by fungi such as Alternaria, Cercospora,
Septoria, and other fungi. All of these fungal diseases of peony
are favored by wet weather and infections begun in spring may
eventually cause severe symptoms later in summer. Gardeners can
reduce disease in the following ways: increase plant spacing
to improve air circulation and keep humidity lower, prune away
shading vegetation from nearby trees and shrubs, avoid wetting
foliage when watering, remove and destroy diseased foliage and
blighted stems in the fall. Fungicides are available for home
garden use to help prevent peony foliar diseases. Check fungicide
labels for timing and rates to use for peony diseases.
--Dr. John Hartman, Extension Plant Pathologist, University
of Kentucky, Lexington
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