White Pine Blister Rust in British Columbia II. Can Stands be Hazard Rated?

Abstract

Twelve to 30-year-old western white pine (Pinus monticola Dougl.) in 23 stands in British Columbia were surveyed for blister rust (Cronartium ribicola J.C. Fisch. ex Rab.) cankers. Canker length, mid-point diameter, and height above ground were measured. The number of cankers per tree tended to increase with tree diameter, was variable within stands, and on 15 to 20 cm diameter trees ranged from a mean of one to 14 per stand and the overall mean was four cankers per tree. Large branches bore longer cankers and tended to be higher in the tree than small branches which bore short cankers. Incidence of cankers above 2.5 m tended to increase with increasing slope and they were on the side of the tree subject to evening breezes. Based on Idaho standards all sites in British Columbia were rated as low hazard, but trees growing on slopes had a higher risk than those on flat sites.Key words:Cronartium, Pinus monticola, hazard rating