OPERATIONAL CONTROL OF WHITE-PINE BLISTER RUST BY REMOVAL OF LOWER BRANCHES

Line surveys were conducted in 13 young western white pine (Pinus monticola D. Don) stands throughout British Columbia to determine the effectiveness of lower branch removal in controlling blister rust (Cronartium ribicola Fischer). Uninffected trees and most trees with infected branches were protected from future stem infections. In general, effectiveness and efficiency could have been improved by (a) earlier treatment to reduce stem infections, (b) not treating trees with infected stems, (c) treating all other trees, and (d) removing infected branches above the treatment height. Some stands were spaced during treatment; however, untrained fallers failed to distinguish between healthy trees and those with infected stems. Frequently healthy trees were felled while diseased trees were left standing. A pretreatment survey is recommended to determine the level of crew training needed and treatment prescription.