Western Gall Rust Dynamics and Impact in Young Lodgepole Pine Stands in West- Central Alberta

1988

S. 1437-1442

4 Abb., 3 Tab., 20 Lit. Ang.

Unselbständiges Werk

200038773

Canadian Journal of Forest Research 1988 ; 18(11), S. 1437-1442

A sample of 29 405 lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) trees was assessed from 1982 to 1985, and stem analysisdata of 75 trees from five heavily infested second-growth stands in the foothi lls of the Rockies were analyzed to determine the incidence, development, and impact of western gall rust Endocronartium harknessii (J.P. Moore) Y. Hiratsuka,in relation to age of trees and stand and site factors. The incidence of weste rn gall rust increased with stand age and time. In stands up tp 12 years old, the incidence averaged about 5% and increased rapidly to about 20% at age 20. A rapid increase in incidence over time occurred in younger age-classes. In stands 20 years or older, the incidence of new infection was low. Mortality associated with western gall rust among crop trees was low. There was, however, 30% mortality in an unthinned 22-year-old stand over its life. Impact on growth was highly significant. In the periods 11-15 years and 16-20 years after the wave of heavy infection, reductions in volume growth of infected crop trees were 15and 25%, respectively. This loss amount to 15% of the total volume over the 20 -year period during which the stands are affected. Western gall rust incidence was higher in stands on east-facing slopes than on south- and north-facing slopes. Stands at elevations between 1200 and 1400 m had the highest incidence. Forest management strategies to reduce the impact of western gall rust are discussed, with emphasis on spacing that includes sanitary removal of infected trees.