White Pine Blister Rust Attracts Rodents
When a white pine has been infected with white pine blister rust (a fungus), cankers appear on the branches and sometimes the trunk of the tree. A large amount of sap-like ooze flows from the cankered areas, sometime drying and resembling a sugary-looking crust or film. These areas are, in fact, high in sugar content, and rodents frequently chew them. It’s likely that a red squirrel visited and sampled the infected white pine in the photograph, leaving a freshly-gnawed patch in the bark.