The Effects of Arceuthobium americanum Infection on Pinus contorta var. latifolia Needles

Abstract

The lodgepole pine dwarf mistletoe, Arceuthobium americanum, a common parasite found in western Canadian forests, causes significant yearly timber loss. The purpose of this work was to determine if dwarf mistletoe infection of lodgepole pine affects the anatomy and morphology of its needles. Needles were collected from infected, highly-broomed trees and from visibly uninfected (control) trees. Differences in the dimensions of the needles and vascular cylinder, fresh weight, number of stomata per unit surface area (density), size of stomata, stomatal area per unit surface area, and number of rows of stomata were quantified. Needles from infected brooms were shorter, thinner, and narrower with larger, more densely packed stomata.