Relative frequency of bole and branch infection of lodgepole pine by western gall rust

Abstract

Tree height and number of western gall rust (caused by Endocronartiumharknessii (J.P. Moore) Hirat.) bole and branch infections per living tree were recorded in three experimental 7-year-old lodgepole pine (Pinuscontorta Dougl. ex Loud.) plantations located near Fort St. James, Mackenzie, and Fort St. John, B.C. An extra set of data for trees originating from north of 60°N was also taken at Fort St. John. Each plantation consisted of 40 types of genetic material (i.e., different parentage and latitude of origin), while the extra set at Fort St. John consisted of 17 types of genetic material. The 4357 trees examined had an average of 1.81 gall rust infections per tree, and 49.1% of all trees were infected. Ninety percent of all infections originated in a single year (1990). The number of galls per unit target area declined with increasing height above ground. The percentage of galls located on the bole was 3.10, 10.53, 8.03, and 9.88% for the four populations, respectively. The number of western gall rust infections per tree was linearly related to tree height. The number of infections on boles did not vary with tree height, but the proportion of all infections located on the bole was linearly related to the reciprocal of tree height. The proportion of infections on the bole did not vary significantly with infection severity. Finally, the proportion of galls on the bole did not differ significantly between types of genetic material.