This application may be mixed with spray oil for scale and mite control. Apply all chemicals according to directions on the label. This disease can kill branches or trees and is caused by the fungus Botrysphaeria dothidea . Earliest symptoms appear on the young bark of vigorous trees as small blisters, usually occurring at lenticels. Infection occurs late in the season, and may be apparent in the fall or the following spring.
Some infected areas exude a gummy resin.
Large amounts of gummy exudate, or gum balls, are associated with lesions at multiple sites. After repeated infections, the bark becomes rough and scaly. Keep trees healthy, since the most severely infected trees are water-stressed. Dead wood should be removed during winter pruning, and destroyed. When pruning during the summer months, remove and destroy all pruned wood.