White Pine Blister Rust

You'll spot this disease on five-needle white pines, where stem cankers girdled by blistered, resinous bark signal infection. The blister rust attacks the branches and trunk, causing characteristic orange-yellow pustules on Ribes (currant and gooseberry) alternate hosts. In Western Washington, late summer and fall cool, moist conditions favor the spread of spores from infected currants to nearby pines. Infected branches show early defoliation and dieback by mid-summer.

White pine blister rust is devastating to five-needle pines because once the fungus girdles a branch or the main stem, that portion dies. Your tree's ability to recover depends on location of the canker and how quickly you act. The critical management move is preventing infection in the first place by removing currant and gooseberry plants within several hundred feet of white pines, especially in moist, low-air-circulation sites. Plant resistant species or five-needle pines in sites with good air drainage and at least 300 feet from alternate hosts.