Efficacy of Erythropleum suaveolens (potrodom) and Distemonanthus benthamianus (bonsamdua) water extractives on the durability of five Ghanaian less used timber species of varying perviousness and retentiveness

摘要

Conventional wood preservatives are not only toxic to target bio-deterioration organisms but also to humans, other organisms and the environment. In an effort to find preservatives that are less toxic or non-toxic to man, other organisms and the environment, efficacy of branch bark and heartwood water extracts (0.65 g/ml) of Erythropleum suaveolens (potrodom) and Distemonanthus benthamianus (bonsamdua) were tested on five less used species (LUS) namely, Sterculia oblonga (ohaa), Antiaris toxicaria (kyenkyen), Canarium ediwonua), Celtis zenkeri (esa-kokoo) and Cola gigantea (watapuo) of varying perviousness and retentiveness from varying contents of hydrophobic and water-repellent extractives and/or extraneous substances in wood and/or vessels. Bonsandua extracts were more resistant to leaching, but potrodom extractives improved durability of Canarium schweinfur-thii more than bonsamdua extractives. Potrodom bark extracts could be readily employed to preserve nonrecalcitrant low durability timber species such as C. schweinfurthii, and possibly recalcitrant low durability ones such as S. oblonga after some form of pre-treatment and/or under pressure conditions. Improved durability of immersed and brushed LUS was ranked as follows: C. gigantea > C. zenkeri > S. oblonga > A. toxicaria > C. schweinfurthii proving that the natural durability of timber is somewhat dependent on their level of recalcitrance from intrinsic hydrophobic and/or water-repellent extractives and/or extraneous substances. Thoughextracts showed reduced efficacy with time, the use of potrodom extractives for the preservation (control of pests) of nonrecalcitrant low durability wood is promising.