See:
Peony (Paeonia spp.) - Peony Red Spot
Cause Graphiopsis chlorocephala (formerly Cladosporium paeoniae), a fungus that can impact all aboveground tissues and survives in stem and leaf debris. It has been reported from Washington and found in Oregon. Infection of peony can occur from 50°F to 82°F but the latent period increases as the temperature declines. Free moisture is necessary for conidial germination and infection.
Symptoms Infection of young succulent tissues will limit symptoms to flecking while infection of more mature tissues results in large, expanding lesions.
Leaves-dark purple glossy spots on upper leaf surfaces, dull chestnut color on undersides. Infection is most pronounced at leaf margins, especially near the tips, and slight distortion may occur as growth continues. Outer leaves usually are attacked first.
Stems-on young stems, elongated reddish brown streaks with slightly diffuse margins. As growth continues, lesions near the plant crown tend to coalesce, darken, and become somewhat depressed. Infection spots are abundant at branch and petiole bases where debris of infected parts may have lodged.
Cultural control
- Plant resistant cultivars.
- Space plant for good air circulation.
- Remove old tops in fall or early spring before new growth appears. Cut old stems at ground level and destroy.
Chemical control
- Banner MAXX at 5 to 8 fl oz/100 gal water. Although not listed for this pest, it may be effective. Group 3 fungicide. 12-hr reentry.
- Broadform at 4 to 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Orkestra at 4 to 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Postiva at 10 to 28 fl oz/100 gal water. Group 3 + 7 fungicide. 12-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
Reference Braun, U., Crous, P.W., and Schubert, K. 2008. Taxonomic revision of the genus Cladosporium s. lat. 8. Reintroduction of Graphiopsis (= Dichocladosporium) with further reassessments of cladosporioid hyphomycetes. Mycotaxon 103:207-216