In vitro antifungal activity of cassia fistula leaf extracts against major phytopathogenic fungi

Fungal phytopathogens are responsible for substantial crop losses worldwide, and continued reliance on synthetic fungicides has raised concerns regarding resistance development and environmental safety. This study evaluated the in vitro antifungal activity of aqueous, methanolic, and acetone leaf extracts of Cassia fistula against four economically important phytopathogenic fungi (Alternaria, Cercospora, Colletotrichum, and Fusarium). Antifungal efficacy was assessed using the poisoned food technique on potato dextrose agar, and mycelial growth inhibition was recorded at 3 and 5 days after inoculation (DAI). All extracts inhibited fungal growth in a concentration-dependent manner, with methanolic extract showing the highest inhibitory activity, followed by acetone and aqueous extracts. Inhibition increased with incubation time and was generally greater at 5 DAI. Alternaria and Cercospora were more susceptible than Fusarium. These findings demonstrate that C. fistula leaf extracts possess significant antifungal potential and support their further evaluation as botanical fungicides for sustainable management of fungal plant diseases.