Incidence of Sooty Blotch and Flyspeck on Apple (Malus domestica) in Mambilla Plateau, Taraba State

Apple (Malus domestica) cultivation on the Mambilla Plateau of Taraba State represents a unique temperate fruit production system in Nigeria, supported by cool highland conditions atypical of the broader West African climate. Sooty blotch and flyspeck (SBFS) diseases, caused by complex assemblages of epiphytic fungi, are considered primarily cosmetic but contribute to commercially important reductions in fruit marketability. This study investigated the incidence and distribution of SBFS on apples across five orchard communities on the Mambilla Plateau during the 2023 fruiting season. Thirty-two orchards were assessed, with disease incidence and severity rated using internationally standardised SBFS scoring guides. Fungal isolations from affected fruit yielded Ramichloridium and Zygophiala species as the predominant SBFS fungi, consistent with the taxonomic diversity commonly reported in cool temperate apple environments. Overall SBFS incidence was 71 percent at the commercial harvest stage, with higher rates recorded in orchards surrounded by dense native forest vegetation serving as reservoirs for fungal inoculum. Growers using copper-based fungicide programmes showed lower SBFS incidence compared to untreated controls. Limited access to approved registered fungicides and post-harvest waxing facilities was identified as a structural constraint on disease management in this remote farming community. The study recommends investment in post-harvest infrastructure and a formal fungicide evaluation trial for SBFS management on the Mambilla Plateau. Keywords: apple, sooty blotch, flyspeck, Mambilla Plateau, disease incidence.