RMRS Online Publication
RMRS-RP-36: Frequency of comandra blister rust infection episodes on lodgepole pine

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Jacobi, William R.; Geils, Brian W.; Taylor, Jane E. 2002. Frequency of comandra blister rust infection episodes on lodgepole pine. Res. Pap. RMRS-RP-36. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 13 p.

Comandra blister rust is a damaging canker disease of lodgepole pine in the Central Rocky Mountains. Our knowledge of previous blister rust outbreaks and the effects of weather and climate on rust epidemiology has not been sufficient to explain the frequency and severity of disease outbreaks. Thus, we sought to describe the seasonal and annual frequency and duration of meteorological conditions favorable for infection of lodgepole pine, to relate infection episodes to various weather phenomena, to observe new canker appearances on young trees, and to age existing cankers on mature trees. We examined comandra blister rust outbreaks for three areas in the Central Rockies-Beaverhead in southwestern Montana, Shoshone in western Wyoming, and Medicine Bow in south-central Wyoming. We defined periods suitable for comandra blister rust infection of lodgepole pine (potential infection episodes), based on published criteria, and identified as continuous periods longer than 6 hours during the months of July, August, and September when temperature ranged between 10 and 20 C and the air was nearly saturated. Synoptic daily weather maps were examined to classify weather systems associated with potential infection episodes. We also observed canker establishment on young and mature lodgepole pine trees to determine canker age distributions. Meteorological records indicated that weather conditions considered suitable for infection of lodgepole pine occurred at least every few (~3) years. The frequency, but not the duration of potential infection episodes, were related to the prevailing summer weather patterns within various regions of the Central Rocky Mountains. The pattern of infection observed in one young stand for 8 years was like that which would result from several, sequential wave years. We found no evidence in the age distribution of bole cankers for only one comandra blister rust outbreak in the three study areas. A consistent pattern between meteorological and canker age data indicates that infection occurs frequently enough across the Central Rocky Mountains that comandra blister rust can be considered a continuing threat where populations of comandra and lodgepole coexist.

Keywords: climate, weather, meteorology, risk rating, spore dispersal

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Title: RMRS-RP-36: Frequency of comandra blister rust infection episodes on lodgepole pine
Electronic Publish Date: July 16, 2003
Last Update: July 16, 2003

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