Informational table showing disease name, symptoms, pathogen/cause, and management of Cotoneaster diseases. Disease Symptoms Pathogen/Cause Management Botryosphaeria canker Leaves on affected branches wilt and die. Branches die back and become covered with dark brown to black, pimple-like fungal fruiting structures. Wood under the bark is dark brown. Botryosphaeria Trees most susceptible are those under drought stress. Therefore, irrigate to prevent drought stress. Prune infected branches. Fire blight Infected flowers are killed and often remain attached throughout the season. The ends of twigs and branches become brown or black and may curl over into a shepherd's crook shape. Dead leaves may remain attached to the tree. Cankers formed the previous season may ooze a cloudy liquid during wet spring weather. Branches will be killed as slightly sunken cankers enlarge into larger branches and even into the main trunk. Erwinia amylovora During dormancy when the weather is dry, prune infected branches, cutting at least 4 inches below the base of the canker. Disinfest pruning tools frequently. Fertilize carefully to avoid promoting excessive succulent growth. Remove root suckers and water sprouts while they are small. Remove nearby unwanted plants that are susceptible to fire blight.

Fire blight-resistant plants include Cotoneaster anoenus, C. adpressus, C. canadensis, C. dammeri var. radicans, C. horizontalis, C. microphyllus, C. praecox, and C. zabelii.

Fire blight on hawthorn (above) appears very similar on cotoneaster.

Prepared by Gary W. Moorman, Professor of Plant Pathology