EFFECTS OF COMANDRA BLISTER RUST ON GROWTH AND SURVIVAL OF LODGEPOLE PINE

Comandra blister rust, caused by the fungus Cronartium comandrae, redu ced growth and survival of lodgepole pine trees (Pinus contorta subsp. latifolia) in the central Rocky Mountains. Stem analyses were used to determine annual increments of total cubic bolewood volume for 74 lod gepole pine trees 4-22 m tall, cankered by comandra blister rust. Mean annual increments after canker establishment were reduced 32% for tre es with crown tops killed by comandra blister rust (spiked) and 9% for trees not yet girdled. Volume increments of spiked trees decreased ea ch year after canker establishment until crown loss (top-kill) occurre d; afterward, increments remained small and constant. Bolewood in spik ed trees was sound but split and cracked above the canker. Reductions in radial increments for 140 spiked trees decreased with tree age when they were top-killed and increased with severity of crown loss, measu red as the proportion of stem length above canker center. Total and sa pwood basal areas, crown ratio, and basal area increment were highly c orrelated among spiked trees. Sixty percent of 2,070 trees on either t emporary or monitored plots survived top-kill; percent survival increa sed with canker height. On 15 remeasured plots, no spiked trees with c ankers higher than 13 m had died during the past 5 yr; trees with cank ers lower than 13 m died at rates inversely proportional to canker hei ght. Functions describing expected reductions in radial increment and survival can be incorporated into stand-growth and yield models to pro vide better estimates of disease effects.