Natural decay resistance of some Ghanaian timbers and wood decay hazard potential for Ghana

Abstract

The natural decay resistance of 30 Ghanaian wood species, the decay capacity of four wood decay fungi, the effect of test method on fungal decay ability, and the wood decay hazard potential in Ghana were determined. Five of the wood species were rated as highly resistant, six as resistant, eight as moderately resistant and 11 as non resistant. Of the four decay fungi, Coriolopsis polyzona, Oligoporus placentus, Pycnoporus sanguineus and Trametes versicolor, only the strain of C. polyzona (004) induced adequate weight loss in the birch reference wood in either test methods (agar- and soil-block) for use in decay resistance rating. The two methods significantly influenced the performance of the fungi after 6 weeks of exposure with the white rot fungi showing higher decay ability in soil- than agar-block method, the converse was true for the brown rot fungus (O. placentus) using Betula alleghaniensis as substrate. However, after 12 weeks of exposure the test methods did not seem to have any effect on the performance of the fungi and resultant decay rating. Wood decay hazard in Ghana varies from areas of moderate, to those of very high potential. Generally the western part of the country has higher hazard potential than the eastern portions and the south has higher potential than the north, except for the southeastern comer which has the lowest hazard potential. Rainfall amounts, and to some extent the relief of the area, were the paramount determinants of the decay index in Ghana rather than temperature.