[From The Complete Book of Roses
, by Gerd Krüssmann, 1981, p. 123:]
. Symptoms: the green bark of the previous years's stems develops reddish-brown or purple oval shaped spots. These later turn brown, and spread as the disease develops. In severe cases the stem will collapse and die. Source: Fungus Coniothyrium wernsdorfiae
Laubert. Most common in spring and late summer and resulting from damage to stem either from wounds or frost. Heavy applications of wet manure late in the season may also contribute to infection....Protection: Careful pruning followed by spraying...
. Symptoms: Similar to Coniothyrium
. Source: Fungus Leptosphaeriae coniothyrium