Leptographium terebrantis inoculation and associated crown symptoms and tree mortality in Pinus taeda

Abstract

Leptographium terebrantis has been implicated as a contributing factor of P. taeda decline and mortality over the past several decades. We examined the potential of L. terebrantis to cause decline symptoms and determined the relationship between pathogen spread and the formation of new sapwood. The study was undertaken in a 13-y-old P. taeda plantation using artificial inoculations of fungal-colonized, sterilized toothpicks. We found that L. terebrantis was not only re-isolated from dying inoculated trees but caused decline symptomology and mortality at a high inoculum density. It was found that 20% mortality and severe growth loss among surviving trees occurred with L. terebrantis infection at the high density. At lower inoculum densities, trees produced a complete ring of new sapwood that appeared to sustain tree physiology. This suggests that management practices in P. taeda plantations which minimize bark beetle infestation and pathogen inoculum densities allow adequate sapwood function for sustained growth. • Leptographium terebrantis causes P. taeda tree mortality at high inoculum density. • Some P. taeda trees, however, tolerate the fungus at high inoculum density. • At lower inoculum densities, P. taeda completely tolerates L. terebrantis infection. • Tolerant trees form a continuous or partial sapwood without the fungal infection.