Black Spot of Rose—Diplocarpon rosae
Black spot is caused by a fungus that overwinters on living or dead plant tissue that was infected in the previous growing season. The fungus attacks the leaves, causing yellowing and defoliation, and sometimes attacks the flowers and stems. Defoliation causes the plants look bare and straggly and gives them less energy to produce flowers.
Circular black spots, usually with fringed margins, on the leaves. Spots may coalesce to make large irregular spots.
Spores produced on the old plant material are splashed up on to young plant tissue.
Stems may have purplish red to black lesions.
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Identification and Control Information
- Report on Plant Disease: Black Spot of Rose (PDF)—University of Illinois Extension
- Fact Sheet with Symptoms, Management Options and Resistent Varieties (PDF)—The Ohio State University Extension
[Photos, left to right: Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org; Yuan-Min Shen, Taichung District Agricultural Research and Extension Station, Bugwood.org; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org]