Assessment of the fungicidal effect of <i>Tithonia diversifolia</i> leaf extract on rubberwood (Hevea brasiliensis Müll. Arg.).

Abstract

This study was carried out to assess the fungicidal effect of Tithonia diversifolia (sunflower leaves) extract as a preservative material against fungal attack on rubberwood. The wood samples were cut into sample size of 20mm×20mm×9mm then oven dried at 103°C until constant weight was attained. The wood samples were treated with extracts of sunflower leaves prepared through three methods (methanol, hot water and cold water) and absorption and retention of extracts by wood samples were calculated. After treatment, the wood samples were exposed to three fungal species including Phanerochaete chrysosporum (white rot), Serpula lacrymans (brown rot) and Gilbertella persicaria (soft rot) for a period of 8 weeks followed by the assessment of weight loss. The result obtained revealed that hot water extract had the highest (40.84%) of preservative absorption by the rubber wood, while cold water extract indicated the least quantity (35.23%). The wood treated with methanol extract had the highest retention value of 3.52% while the lowest value was reported for the wood treated with cold water extract with 2.12%. Results obtained revealed that there was no significant difference (p>0.05) in the percentage weight loss of the treated and untreated wood samples. Untreated rubber wood samples had the highest percentage weight loss of 15.51% followed by cold water extract treated wood samples (14.17%) and samples treated with hot water extract (10.73%), while the least was recorded for wood samples treated with methanol extract (10.19%). These results implied that rubber wood samples treated with methanol extract exhibited only a minimal resistance to fungi, while the untreated wood samples exhibited the highest percentage weight loss. Therefore, it is clear that Tithonia diversifolia leaf extract did not give considerable protection to rubber wood against fungi attack due to the low content of tannin and flavonoid present in the leaves which could inhibit fungal growth, and there is a need for further research to find suitable bio preservatives for rubber wood.