The fungus grows beneath the protection of the leaf cuticle, making control difficult once the spores have germinated. Weekly sprays from the time the plant leafs out in the spring until autumn are advised. Spray both the upper and low leaf surfaces. Proper pruning will remove spores overwintered in small cane lesions. Stem cankers appear as small lesions on the woody tissue of canes.
Results are poor growth of the affected area and eventual death of the cane.
Stem canker is caused by several different parasitic fungi entering the stem through wounds or dying tissue. Brand canker appears as black sooty patches that develop during winter on climbing roses and those covered for winter protection. Cracking bark is common. The best control is pruning out the infected canes. Brown canker appears as light brown lesions with deep purple margins.