Stem cankers rose

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. This fungus will
also attack foliage and buds on some cultivars. It is not
common if a fungicide program is followed for control of
other rose diseases. Stem canker appears as black spots, often
at the point of mechanical damage. It is somewhat reddish and
becomes brown, sunken and cracked with age. Cankers often
appear on plants weakened due to black spot.
The most effective means of preventing the problem is to
maintain a preventive fungicide spray program to control other
fungal diseases. Should cankers appear, prune the cane well
below the canker with clean pruning shears.