Fire Blight (bacterium –Erwinia amylovora): New shoots suddenly appear as if scorched by fire. Brown or blackened leaves cling to twigs. Slightly sunken, girdling, discolored cankers on twigs, branches and trunk. Prune and burn affected parts.
Leaf Spots (fungi – Entomosporium maculatum, Phyllosticta cotoneastri): With Phyllosticta, leaves will have reddish-brown spots bordered by darker zones, outside of which is a zone of dark red. There may also appear within the spots small, black fruiting structures of the fungus.
Canker (fungus – Physalospora obtusa): This fungus causes cankers and twig blight on cotoneaster. Prune and destroy infected branches.
Cotton Root Rot (fungus – Phymatotrichum omnivorum): (See the section on Cotton Root Rot)