Leaves have yellow or orange powder on them.

Underside of the leaves have orange spores in the summer or fall.

White Pine Blister Rust

Ribes leaves after laboratory inoculation with white pine blister rust.
Photo courtesy of Paul Zambino, USDA Forest Service, Rhinelander, Wisconsin

White pine blister rust uridia (orange) on the under surface of black currant 'Ben Alder' growing in a field in Corvallis, Oregon.

White pine blister rust teliospore (brown/black) production at the end of the summer on Ribes valdivianum Phil. cultivated in Corvallis, Oregon.

White pine blister rust infecting western white pine (Pinus monticola D. Don.).

• Causal Organism: Cronartium ribicola J.C. Fischer; Asia, Europe, North America.
• Crops Affected: Black, red, white and ornamental currants, gooseberries, species.

The rust alternates between 5 needle pines and Ribes. Aecial spores travel from the pines in spring and early summer and infect Ribes leaves. The spores from pine can travel over 300 miles, and survive for 4 months under optimal conditions. Orange uredia form on susceptible Ribes cultivars. Uredinial spores infect other Ribes. At the end of the summer or early fall, brown or black spores (teliospores) form at the edge of the orange pustules. Additional spores are formed that can infect pines. These spores generally do not travel more than 1000 feet.

Warm moist conditions are required for all spore stages to cause an infection.

Also see: Description and control information for white pine blister rust on Pine from Oregon State University.