Relationships among jack pine budworm damage, selected tree characteristics, and Armillaria root rot in jack pine

Abstract

Trees in a 94-year-old jack pine (Pinusbanksiana Lamb.) stand defoliated by the jack pine budworm (Choristoneurapinus Freeman) were examined to see if there was an association of root condition and stem growth with tree condition. Healthy trees had heavier root systems, larger root volumes, and larger annual volume increments than top-killed or dead trees in the years prior to elevated tree mortality within the stand. Roots of all the dead trees contained Armillariaostoyae (Romag.) Herink (North American Biological Species I). Three of five top-killed trees and one of five healthy trees were infected by A. ostoyae. There was no clear indication whether infection by root pathogens determines the extent to which trees are damaged following jack pine budworm defoliation, or conversely, whether repeated defoliation predisposes trees to root pathogen attack. Numbers of live branches in the crown, radial increment over the past 10 years, and prevalence of Armillaria root rot within a stand may be used to hazard rate stands prior to budworm outbreaks. The management implications of the results are discussed.