Cankers are formed where the fungus has become established in the bark through wounds. These may be open and look like targets with concentric circles, or be closed with only a horizontal slit showing at the surface.
Cankers can develop on twigs, branches, or the main trunk.
Removal of infected twigs and branches helps to reduce the spread of the fungus into the main trunk and may slow the spread of infection. Additionally, it is important to maintain tree vigor with adequate water and fertilizer in the spring. There is no known control. Insect Problems Aphids. Of the many species of aphids, two are very common.