Peony leaf blotch
Karen Rane, Sr. Plant Disease Diagnostician, Department of Botany
& Plant Pathology, Purdue University
Leaf blotch, also called red spot and measles, is
a common disease of peony caused by the fungus Cladosporium
disease has multiple names because there are multiple symptoms
- lesions occur on leaves or stems, and vary from tiny red
spots (“measles”) to larger brown or purple blotches.
The fungus survives the winter in infected plant debris, and produces
spores in the spring which are splashed onto young foliage and
stems through rainfall or overhead irrigation. Although symptoms
are quite striking, and infection can be very severe, the impact
of this disease on plant health and survival appears to be minor.
Sanitation (removing dead plant residues in late fall or early
spring before plants break dormancy) is important in reducing the
severity of this disease in the home garden. Use drip irrigation
rather than overhead sprinklers when watering peony plants, to
avoid wetting the foliage and providing a favorable environment
for disease development.
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