Survival, Frost Susceptibility, Growth, and Disease Resistance of Corkbark and Subalpine Fir Grown for Landscape and Christmas Trees

Abstract

Trees from six corkbark fir (Abies lasiocarpa var. arizonica) and 10 subalpine fir (A. lasiocarpa var. lasiocarpa) seed sources were grown at the University of Idaho Sandpoint Research and Extension Center (SREC), Sandpoint, ID, and two commercial nurseries in Idaho and Oregon. Posttransplant mortality was highest during the first two years. After six growing seasons, survival averaged 76% and 80% for corkbark and subalpine fir, respectively. In SREC irrigated plots, survival averaged 96% and 99% for corkbark and subalpine fir, respectively. Spring frost damage occurred annually on 66% to 100% of trees during 2002–06. In SREC plots, damage was minor and did not adversely affect appearance. Tree heights and growth rates varied significantly between seed sources. In general, corkbark fir grew faster than subalpine fir. After nine years in the field, mean heights of SREC-grown corkbark trees ranged from 2.1 to 2.9 m and that of subalpine trees ranged from 1.3 to 2.3 m, depending on seed source. Corkbark fir proved moderately resistant to resistant to a phoma-type fungal blight. Three corkbark seed sources appeared suitable for Christmas tree production. Subalpine trees were more susceptible to the blight. Some trees within both botanical varieties proved resistant to or highly tolerant of the blight, but the use of seedlings for landscapes may be unacceptably risky because of disease potential. Two fungicide programs (three applications of pyraclostrobin plus boscalid or one application of pyraclostrobin plus boscalid followed by one application of chlorothalonil) controlled the blight. Eight subalpine fir and 23 corkbark fir at SREC were selected for further testing as possible cultivars. Neither crop is recommended for sites with frequent or severe spring frosts.