Inhibition of fungi with wood extractives and natural durability of five Cameroonian wood species

The natural durability of five Cameroonians wood samples was evaluated using the European standard EN 350-1 with a slight modification. The capacity of extracts to inhibit the fungal growth was evaluated at different concentrations with propiconazole (a commercial fungicide for wood) as standard. Scanning Electron Microscopy (SEM) of wood blocks was carried out before and after extraction in different solvents. Unextracted and extracted wood blocks were exposed to fungal attack, with beech as a reference wood. Results showed that mass losses of non-extracted samples ranged from 0.1 to 59% and those of extracted samples from 3% to 40%. Before extraction, all wood samples under study were classified as very resistant to fungi attack (class 1) with respect to the standard. After extraction, some of the wood samples became vulnerable to fungal attack. Movingui, padouk, and tali became less resistant to fungi attack (class 3). The SEM of wood revealed that the extractives were removed from the fibres. The effect of extractives on fungal growth showed that extracts weakly inhibited fungal growth up to concentrations of 250 μg/mL but extracts of tali and movingui totally inhibited fungal growth at a concentration of 500 μg/mL.