. The Canadian field-naturalist. 1982 POWELL: Damage to Pine Stem 289 Rodent Damage on Comandra Blister Rust Cankers in Southwestern Alberta Methods and Materials During studies of the biological factors affecting aeciospore production of Comandra Blister Rust cankers on Lodgepole Pine, observations were made on the frequency and damage of fresh and old rodent chewing. Other biological factors affecting aeciospore production have already been reported (Powell 1971a, b, c; 1974). Observations were made from 1966 to 1972 at 24 locations between latitudes 49°45' and 52° 10' north (Figure 1
. The Canadian field-naturalist. 1982 POWELL: Damage to Pine Stem 289 Rodent Damage on Comandra Blister Rust Cankers in Southwestern Alberta Methods and Materials During studies of the biological factors affecting aeciospore production of Comandra Blister Rust cankers on Lodgepole Pine, observations were made on the frequency and damage of fresh and old rodent chewing. Other biological factors affecting aeciospore production have already been reported (Powell 1971a, b, c; 1974). Observations were made from 1966 to 1972 at 24 locations between latitudes 49°45' and 52° 10' north (Figure 1). A total of 448 tagged cankers were followed for rodent feeding; 347 were tagged in 1966 or earlier, and 101 were tagged in 1967. The number at any one location varied from 1 to 48. The trees varied in age from 3 to 125 years at time of tagging. By 1972 only 183 trees that had borne cankers in 1966 or 1967 were still alive, most having been killed by the rust. Ninety-five percent of the cankers were located on the main stem, with an average aboveground height of 35 cm to the center of the canker. The few branch cankers were also generally close to the ground. The average length of the stem cankers was 47 cm, making them accessible to feeding by lagomorphs and ground rodents, especially since many cankers reached ground Figure 1. Locations in southwestern Alberta where rodent damage on cankers of Comandra Blister Rust was studied, 1966-72. During most years the percentage of new chewing was recorded and its possib.'e effect on future aecial production was noted. Some observations in 1968 and all in 1971 recorded the total percentage of cankered bark removed by rodents. To obti^in this percentage, scaled drawings were made of eaci? canker and the area of bark removed by the rodents. A few locations were visited weekly or more frequently through the sporulation preiod (early May to Septemtber); others were visited once or twice a year. Results and Discussion Rodent fee
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