Sapwood growth and tolerance of Pinus taeda trees to Leptographium terebrantis inoculation

Abstract

Leptographium terebrantis is an opportunistic root pathogen that has been implicated as a contributing factor of Pinus taeda decline and mortality over the past several decades in central parts of Alabama and Georgia, USA. We assessed the potential of L. terebrantis to initiate crown thinning in young P. taeda trees and hypothesized that L. terebrantis infestation will impose moisture stress on foliage, induce premature senescence, and cause loss of foliage biomass. The study was undertaken in a naturally regenerated 5–7‐year‐old P. taeda stand at Andalusia, Alabama in a completely randomized design using artificial inoculations of L. terebrantis colonized toothpicks. After four years of infestation, the pathogen caused sapwood occlusions and loss of sapwood function but failed to impose moisture stress on needles to induce premature senescence and loss of biomass. The new sapwood formed around the occluded area was devoid of pathogen infestation. The new growth was approximately twice the size of occluded tissue and compensated for the loss of old sapwood function to sustain tree growth. Results demonstrated that young P. taeda trees can tolerate L. terebrantis infection when stand conditions sustain the formation of new sapwood.