Journal of Chemical Ecology, Vol. 21, No. 5, 1995 EFFECTS OF BIOTIC AND ABIOTIC STRESS ON INDUCED ACCUMULATION OF TERPENES AND PHENOLICS IN RED PINES INOCULATED WITH BARK BEETLE-VECTORED FUNGUS KIER D. KLEPZIG, ]'3 ERIC L. KRUGER, 2 EUGENE B. SMALLEY, I and KENNETH F. RAFFA 3 IDepartment of Plant Pathology 2Department of Forestry 3Department of Entomology University of Wisconsin-Madison Madison, Wisconsin 53706. (Received October 10, 1994; accepted January 31, 1995) Abstract--This study characterized the chemical response of healthy red pine to artificial inoculation with the bark beetle-vectored fungus Leptographium terebrantis. In addition, we sought to determine whether stress altered this induced response and to understand the implications of these interactions to the study of decline diseases. Twenty-five-year-old trees responded to mechanical wounding or inoculation with L. terebrantis by producing resinous reaction lesions in the phloem. Aseptically wounded and wound-inoculated phloem contained higher concentrations of phenolics than did constitutive tissue. Trees inoculated with L. terebrantis also contained higher concentra- tions of six monoterpenes, c~-pinene, 13-pinene, 3-carene, limonene, cam- phene, and myrcene, and higher total monoterpenes than did trees that were mechanically wounded or left unwounded. Concentrations of these monoter- penes increased with time after inoculation. Total phenolic concentrations in unwounded stem tissue did not differ between healthy and root-diseased trees. Likewise, constitutive monoterpene concentrations in stem phloem were sim- ilar between healthy and root-diseased trees. However, when stem phloem tissue was challenged with fungal inoculations, reaction tissue from root- diseased trees contained lower concentrations of ct-pinene, the predominant monoterpene in red pine, than did reaction tissue from healthy trees. Seedlings stressed by exposure to low light levels exhibited less extensive induced chem- ical changes when challenge inoculated with L. terebrantis than did seedlings growing under higher light. Stem phloem tissue in these seedlings contained *To whom correspondence should be addressed at USDA Forest Service, 2500 Shreveport Hwy., Pineville, Louisiana 71360. 601 0091]-0331/95/05fl0-0601$07.50/0 © 1995PlenumPublishing Corporation