Professional Evaluation of Wood Decay Fungi on Iroko Timber (Milicia excelsa) in Forest Reserves in Ondo State, South West Nigeria

Iroko (Milicia excelsa) is among Nigeria's most commercially valuable timber species, yet wood decay caused by basidiomycete fungi poses significant threats to standing timber quality in forest reserves and plantation settings. In Ondo State, which maintains several commercially productive forest reserves, systematic assessment of wood decay fungi on iroko has not been formally documented at a professional level. This study evaluated the occurrence, identity, and economic significance of wood decay fungi on iroko timber in three forest reserves in Ondo State during 2023. Fifty iroko trees showing external signs of fungal infection, including basidiocarps, internal cavities, and pileus structures, were sampled. Fungal sporocarps and wood decay columns were examined using morphological and molecular phylogenetic methods, resulting in the identification of Ganoderma applanatum, Phellinus noxius, and Fomes fomentarius as the principal wood decay species. Internal decay extent was estimated by resistance drilling, revealing average decay column widths of 12 to 37 centimetres in heavily infected trees. Trees in stands with higher basal wounding from logging operations showed significantly greater decay incidence, confirming wound entry as the primary infection pathway. Economic valuation of decay-affected timber volume estimated losses at approximately 2.3 million naira per hectare of severely affected reserve. The study recommends wound management protocols during selective logging operations and exclusion of heavily infected trees from commercial timber harvesting. Keywords: Iroko, wood decay fungi, Ganoderma, forest reserve, Ondo State.