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Pathological Pruning: A Useful Tool in White Pine Blister Rust Control. George F. Lehrer, Plant Pest Specialist, Plant Industry Division, Wisconsin Department of Agriculture, Trade and Consumer Protection, Antigo 54409. Plant Dis. 66:1138-1139. Accepted for publication 24 March 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-1138.

Paired-tree plots were used to determine the advantages of pathological pruning, in which all lower branches are removed from young eastern white pines (Pinus strobus), as opposed to removing only cankered branches. After 9 yr, pathological pruning was nearly three times more effective than canker pruning because many latent infections were removed, and the preventive effect has been significant. Pruning cankered branches only would have saved 10.7% of the pruned trees, and an additional 20.1% were saved by removing all lower branches. Pathological pruning eliminated latent infections on 13.9% of trees and prevented new infections on 6.2%. Total blister rust loss in the unpruned controls was 29.7% compared with only 7.4% in the pruned trees.