Emerging threat of Colletotrichum siamense causing leaf blight in Plectranthus vettiveroides

Leaf blight disease emerges as the most prevalent disease affecting Plectranthus vettiveroides. The onset of leaf blight symptoms manifested initially as water-soaked lesions appearing at the edges of the leaves. Over time, these lesions transformed into ash-brown color with irregular margins. As the disease advanced, the lesions expanded to encompass the entire leaf lamina. On PDA media, the pathogen exhibits robust growth, producing white, aerial, floccoid mycelia. The hyaline, branched and septate hyphae bear bullet shaped conidia with an average size of 7.73 × 2.9 μm. Molecular characterization using ITS primers (ITS-1F/ITS-4R), followed by sequence analysis in the NCBI database, conclusively identifies the pathogen as Colletotrichum siamense. Hence, this study is the first report of Colletotrichum siamense causing leaf blight in Plectranthus vettiveroides.