Annosus root rot caused by the fungus Heterobasidion annosum (fr.) Bref., causes a destructive root and butt rot of many important tree species throughout the world. Presently, methods for determining disease incidence and severity and destructive. In this study, the most effective, non-destructive, disease severity prediction parameters were determined for thinned Pinus taeda plantations growing on high hazard sites. Above-ground tree parameters and 0.03m³ soil-root (SR) samples were used as predictions variables. Base-line data for predictions was obtained by excavations of 190 tree root system from plantations located in Eastern Virginia and Central Alabama. Multiple regression analysis indicated that stem diameter (DBH), radical growth (GR5) live crown ration (LCR), and SR samples were the most effective parameters in explaining the variation in the root sustem colonizatio levels of the plot trees studied. / M.S.

The hypothesis that stressed loblolly pine (Pinus taeda L.) could be distinguished from non-stressed loblolly pine by increased foliage temperatures was tested. The foliage temperatures of seedlings and trees were measured with an AGA Thermovision 680 system, imported by the AGA Corporation, Secaucus, New Jersey. The AGA Thermovision 680 system is a simple, easily transported remote sensing system for detecting relative apparent temperatures of plant foliage without direct contact with the leaves. This system is sensitive to infrared wavelengths in the 2-5.6 micron region of the electro-magnetic spectrum. Foliage temperatures in loblolly pine seedlings increased within one week of stress induced by drought, flooding, or severing. Increased temperatures of stressed seedlings were associated with reduced needle moisture content prior to visual symptoms of stress. Foliage temperatures of loblolly pine trees stressed by severing the bole were warmer relative to neighboring control trees. Increased temperatures were detected within one week after severing. Previsual detection of stress can be achieved by measuring foliage temperatures of loblolly pine. The AGA Thermovision should prove to be a useful tool for non-destructive sampling of plant stress, for locating stressed trees, and potential bark beetle infestations. / Ph. D.