Effects of Partial Girdling on Growth in Lodgepole Pine with Application to Damage by the Weevil Hylobiuswarreni Wood

Abstract

Leader growth and radial increment on the stem and main lateral roots during three consecutive years following partial girdling treatment were analyzed on 25- to 30-year-old lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) from a natural stand in west-central Alberta. Simulation of the larval feeding wounds of the weevil, Hylobiuswarreni Wood, consisted of the removal of a 7-mm-wide band of bark from 0% (control), 20%, 40%, 60%, 80%, and 90% of the root-collar circumference of 58 sample trees.Partial girdling reduced leader elongation and radial increment of the leader and lateral roots. Leader height decreased with increased girdling of the root-collar during each of the three post-treatment years. Below the leader, partial girdling of the root-collar did not affect radial increment in the first year, caused an increase during the second year, and a decrease in the third year. At 2 cm above the partial girdles, radial growth above the girdled side of stems was always less than that on the nongirdled side and showed a trend of increase with increased girdling on both girdled and nongirdled sides of the stem. Radial increment was considerably reduced on lateral roots extending below girdle wounds during the three post-treatment years. Two graphs are prepared which can be used to estimate height and radial increment losses in young pine stands infested by H. warreni.