Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 10, 2003
Publication Date: December 30, 2003
Citation: Morales Ramos, J.A., Rojas, M.G., Hennon, P.E. 2003. Black-staining fungus effects on the natural resistance properties of alaskan yellow-cedar to the Formosan subterranean termite (Isoptera: Rhinotermitidae). Environmental Entomology. 32:1234-1241. Interpretive Summary: Alaskan yellow cedar has been reported to possess characteristics that give it a significant degree of resistance against the attack by the Formosan subterranean termite. Some laboratory studies have shown that Alaskan yellow cedar wood can cause death to termite groups and reduce the rate of feeding of termite workers. Alaskan yellow cedar wood has a high content of the chemical nootcatone, which is known to possess insecticidal and feeding deterrent properties against subterranean termites. The use of Alaskan yellow cedar in construction may help to reduce losses due to termite damage. A proportion of the commercially available Alaskan yellow cedar timber shows the presence of black stains produced by a fungus, which has not been identified. The effects of black stains on the natural resistance of commercial Alaskan yellow cedar against subterranean termites has not been assessed. The objective of this study was to determine if the presence of black stain in Alaskan yellow cedar compromises its value as a termite resistant wood. In a no-choice study, groups of termites were fed wood blocks of either unstained, partially black stained, or totally black stained Alaskan yellow cedar. Blocks of loblolly pine were fed to a control group for comparison. Mortality and feeding rates were compared among the termite groups feeding on the different woods. Unstained and black stained Alaskan yellow cedar wood was chemically analyzed in a gas chromatograph to compare their chemical composition. Termite groups feeding on unstained Alaskan yellow cedar showed higher mortality and lower feeding rate than groups feeding on black stained (partially of totally) Alaskan yellow cedar or pine wood. Termite feeding rates increased proportionally to the degree of black stain on the Alaskan yellow cedar. Chemical analysis showed that black stained Alaskan yellow cedar wood has ¼ the concentration of nootkatone as unstained cedar wood. However, even fully black stained Alaskan yellow cedar produced significantly more mortality of termite groups and showed less feeding damage than the loblolly pine control. This shows that the presence of black stain significantly reduce, but do not eliminate, the termite resistant properties of Alaskan yellow cedar wood.
Technical Abstract: The effects of a black wood stain, caused by one or more fungi, on the natural resistance of Alaskan yellow-cedar (AYC), Chamacyparis nootkatensis (D. Don) Spach, to the Formosan subterranean termite, Coptotermes formosanus Shiraki, were studied. Feeding and survival of groups of 300 C. formosanus feeding on unstained Alaskan yellow-cedar heartwood and sapwood, and fully and partially black stained heartwood were compared to a control group feeding on loblolly pine, Pinus taeda L., wood. All termite groups feeding on unstained AYC died by the end of 14 weeks. At the end of 32 wk, mortality of termite groups feeding on fully and partially black stained AYC was significantly higher than that of groups feeding on pinewood. Mortality on the termite groups was significantly higher when feeding on partially than on fully black stained AYC at the end of 32 wk. Wood consumption was significantly different among all treatment groups with means of 4.07, 8.76, 19.81, and 29.77 mg/d in the unstained, partially, and fully black stained AYC, and loblolly pine, respectively. This suggests that toxic and feeding deterrence properties of AYC heartwood were significantly reduced by black stain fungus infection, but were not totally lost. Chemical analysis of unstained and black stained AYC wood showed approximately a 50% reduction in concentration of secondary chemicals in the black stained wood. Carvacrol was totally absent in the black stained wood. Concentrations of nootkatone in the black stained wood were 1/4 of those observed in unstained AYC wood.