Abstract
Loblolly pine, Pinus taeda L., responded to wounding and wounding plus inoculation with two fungal associates of the southern pine beetle (SPB), Dendroctonus frontalis Zimmermann by forming a hypersensitive reaction zone around the wound sites. There was a significant difference in the length of the reaction produced depending upon treatments. A simple mechanical wound produced a shorter lesion than a wound accompanied by inoculation with Ceratocystis minor (Hedgecock) Hunt var. barrussi Taylor which produced a shorter lesion than a wound accompanied by a C. minor inoculation. There was a significant change in monoterpene composition and a significant decrease in soluble sugars present in the hypersensitivereaction zones compared with unwounded phloem, but there were no differences in these parameters between the reaction zones resulting from the two fungal inocula. The overall response of the trees to invasion by SPB fungal associates was a compositional change in potential toxins (monoterpenes) accompanied by a decrease in potential nutrients (soluble sugars) in the area directly surrounding the wound site. Also, the more virulent invader appeared to evoke a stronger response (lesion length) by the trees.