Cankers
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Figure 209. Figure 209. Canker development in aspen begins with discoloration of the bark.

Canker-causing fungi are common on hardwoods, especially aspen. Canker fungi are often the primary cause of aspen mortality because aspen bark is soft living tissue, extremely susceptible to wounding and subsequent infection by canker fungi. Disturbances such as selective logging, campsite construction, and recreation abuse can increase the incidence of canker diseases. Although the majority of canker-causing fungi described below occur on hardwoods, the last fungus discussed occurs on conifers. Canker-causing stem rust fungi are discussed in another section, "Stem and Cone Rusts of Pine."