Effect of burgundy solid extracted from Eastern Red Cedar heartwood on subterranean termites and Wood-decay fungi

Abstract

Eastern red cedar (ERC) is an abundant natural resource in the U.S. and has been investigated for the extraction of cedarwood oil (CWO) and CWO bioactivity, particularly its use to protect wood against termites and decay fungi. Methanol extraction of ERC sawdust gives a burgundy-colored oil (BO) that is comprised of both CWO and a burgundy solid (BS). The BO was significantly more inhibitory against two species of white-rot decay fungi than CWO alone, suggesting the BS itself might have inhibitory bioactivity. This study investigated the wood preservation properties of the BS alone, in combination with CWO and in conjunction with an amylose inclusion complex (AIC) against termites, brown-rot decay fungi and white-rot decay fungi. Wood was treated by vacuum/pressure impregnation and tested for resistance to subterranean termites and four species of decay fungi. The AIC alone made wood less palatable (16% mass loss versus 32% for H2O) and more toxic (32% mortality versus 26% for H2O) to termites but did not inhibit either brown-rot fungi nor the white-rot Trametes versicolor but did inhibit the white-rot Irpex lacteus (49% mass loss versus 65% for H2O). The CWO led to both lower wood mass loss by termites and higher termite mortality as well as having an inhibitory effect on the white-rot decay fungi. However, a combination of AIC and CWO was necessary to have an inhibitory effect on the brown-rot fungi. The addition of BS to the AIC had a minor inhibitory effect on wood mass loss by termites (11% versus 16% for AIC) but did not inhibit either brown-rot fungi nor the white-rot I. lacteus. The addition of BS to the AIC decreased wood mass loss by the white-rot T. versicolor (38% versus 49% for AIC). Wood blocks impregnated with the combination of the AIC, CWO and BS resulted in the highest termite mortality (i.e., 100%), lowest percentage wood mass loss for the termites (i.e., 6%) and lowest percentage wood mass losses for all four species of wood decay fungi studied (less than 20% overall).