Resistivity of ten Nigerian Guinea Savannah Timbers to Lentinus sajor-caju, Sclerotium rolfsii, and Subterranean Termites

Abstract

In this study, the resistivity of Ten Nigerian hardwood trees to fungi and subterranean termites was evaluated through visual and percentage weight loss using standard procedures in the Nigerian Guinea Savannah. The experimental samples were prepared from heartwood and sapwood portions of the species. Fungal decay resistance tests were conducted according to the ASTM D 2017-81 standard method using two fungi species, Lentinus sajor-caju (Fr.) Fries. (white rot fungi) and Sclerotium rolfsii (Curzi) C.C. Tu & Kimbr. (teleomorph) (brown rot fungi). The wood specimens were also exposed to subterranean termites to determine their weight loss due to attack. After exposure, the species were grouped into durability classes based on the weight loss due to resistance of the heartwood to the selected biodeteriorating agents. Lannea welwitschii, Vitellaria paradoxa, Afzelia africana, Albizia zygia, and Syzygium guineense were found to be resistant to both fungi. Khaya ivorensis and Isoberlinia doka were highly resistant to S. rolfsii, and Vernonia colorata was highly resistant to L. sajor-caju. L. welwitschii and Irvingia gabonensis were nonresistant to termite attack unlike their resistance to both fungi, but Anogeissus leiocarpa was highly resistant unlike its moderate resistance to the fungi. K. ivorensis and I. doka were highly resistant to all the biodeteriorating agents. K. ivorensis was ranked best, whereas I. gabonensis was ranked lowest, in terms of their resistance against decay. K. ivorensis showed the highest resistance against termite attack, whereas L. welwitschii and I. gabonensis were nonresistant to termite attack. In general, K. ivorensis exhibited the best natural durability against the selected biodeteriorating agents.