Temporal and Spatial Variation in Infection of Lodgepole Pine by Western Gall Rust. B. J. Van Der Kamp, Department of Forest Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1W5. . Plant Dis. 72:787-790. Accepted for publication 28 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0787.

Variation in infection of lodgepole pine (Pinus contorta) by western gall rust (Endocronartium harknessii) over time was determined by back dating in a 20-yr-old natural stand in central British Columbia. The effect of height, branch order, and aspect within the crown and the influence of stand density on the amount of gall rust infection is described. The year of greatest infection (1976) accounted for 26% and the year of least infection (1982) for 2% of all infections on 370 trees over an 11-yr period. More than 80% of galls were alive 5 yr after infection, but less than 10% 3 yr later. Infection severity in nine heavily galled trees decreased with height aboveground from 1.4 galls per m of branch length at 1 and 2 m above the ground to less than 0.05 at 7 and 8 m. The number of stem infections decreased with height at a similar rate. Branch order and aspect had no significant influence on galls per meter of branch length. Infection did not vary significantly over the range of densities studied (640–2,200 stems per ha). The probability of damaging stem infections decreases rapidly with stand age, and few new stem infections are likely to occur following precommercial thinning.