Selected mechanical and physical properties of Chilean tepa wood affected by butterfly stain

Tepa (Laureliopsis philippiana Looser) is a valuable Chilean temperate hard wood timber species. In anticipation of projected timber shortages in the U nited States, a request has been made to the Animal and Plant Health Inspec tion Service (APHIS) to permit importation of tepa logs. The only known maj or pathogen-related defect is a discoloration of the heartwood known as but terfly stain. This stain, which extends through the length of the bole, app ears in cross section as a series of partially overlapping orange-brown arc s, each limited by a black zone line. The cause of the stain may be a compa rtmentalization-type of response to injury or small branch death and subseq uent invasion by bacteria and/or bacterial invasion through the root system . This investigation examined stained wood versus nonstained wood for possi ble differences in mechanical strength, mineral content, pH, moisture conte nt (MC), and density. Compression (n = 148) and static bending (n = 139) te sts demonstrated that samples from stain-affected trees were significantly weaker than samples from nonaffected trees, regardless of whether the sampl e contained stained wood. There were no differences in shear strength (n = 119). Mineral content and pH suggest no pattern, but post-conditioning MC o f stained and nonstained static bending samples from trees affected by stai n was significantly greater than samples from trees unaffected by the stain . Density of compression samples from stained wood was significantly greate r than that of nonstained samples from stain-affected trees. Data from this research together with a separate bacterial study support the hypothesis t hat tepa wood with butterfly stain has been bacterially degraded and that t his produces a weakened wood matrix.