Effects of cold- and warm-water extractives from decayed and nondecayed western hemlock heartwood on the growth of Fomesannosus

Western hemlock (Tsugaheterophylla (Raf.) Sarg.) heartwood is extremely susceptible to decay by Fomesannosus (Fr.) Karst. Cold-water extracts from nondecayed heartwood mildly inhibited growth of F. annosus in culture, but cold-water extracts from incipient and advanced decayed heartwood stimulated growth slightly. Compounds in cold-water extracts were not identified. Warm-water extracts generally stimulated growth of F. annosus. Phenolic compounds that were extracted by warm-water treatments from nondecayed heartwood were catechin, leucocyanidin, hydroxymatairesinol, and matairesinol. Ultraviolet spectrophotometry and paper chromatography revealed that F. annosus was capable of modifying and (or) utilizing these phenolic compounds. However, concentrated leucocyanidin in culture slightly inhibited growth of F. annosus. The high susceptibility of western hemlock heartwood to decay by F. annosus is apparently related to the absence of strongly fungitoxic heartwood extractives.