Diseases of the tree’s vascular (water-conducting) system generally are not common in the forest or sugarbush. For example, Verticiliium wilt damages mainly urban shade trees. The pathogen is a long-lived, soil-borne fungus. Susceptible trees may become infected if they are planted where diseased ones were removed. The fungus also can be transmitted from tree to tree on pruning tools. It is unlikely, therefore, that Verticillium wilt will constitute a significant forest problem. However, in the sugarbush, the pathogen could be carried from diseased to healthy trees during tapping, especially if infected trees near highways or homes are included among those being tapped. Because the organism is present in the soil, there also is the possibility that infection could occur through root and steam wounds.
Foliage of diseased trees may suddenly wilt at any time during the growing season. A few branches, whole sections of the crown (fig. 101), or the entire crown may show symptoms. Trees with only small portions of crown affected may recover. Those with much or all of their crowns affected probably will die, often rapidly. Stem cross sections show spots or partial to complete circular bands of dark green discoloration involving one or more growth rings (Fig. 102). The discolored streaks may be limited to the trunk or can extend even to the tips of wilting branches.