ANTI FUNGAL ACTIVITY OF CASHEW NUT SHELL LIQUID ON PATHOGENIC FUNGI OF YAM

Yam (Dioscorea spp.) is an economically and nutritionally significant staple crop in West Africa, but its production and storage are severely threatened by postharvest fungal pathogens that cause tuber rot, leading to high quantitative and qualitative losses. Synthetic fungicides are commonly used for control; however, their persistence, high cost, and adverse health and environmental effects necessitate safer and eco-friendly alternatives. This study investigated the antifungal activity of cashew nut shell liquid (CNSL), an agro-industrial byproduct rich in phenolic compounds, against pathogenic fungi of yam. Infected yam tubers were collected from Ega Market, Idah (Kogi State, Nigeria), and fungal isolates were obtained and identified morphologically and microscopically. Pathogenicity tests confirmed four major pathogens: Fusarium oxysporum, Aspergillus niger, Penicillium spp., and Rhizopus stolonifer, with F. oxysporum being the most virulent. CNSL was extracted using Soxhlet extraction with n-hexane and tested in vitro against the pathogens using the food poisoning technique at concentrations of 25%, 50%, 75%, and 100%. Results showed that CNSL exhibited significant, concentrationdependent antifungal activity. At 100% concentration, CNSL completely inhibited the growth of F. oxysporum and A. niger, and achieved near-total inhibition of R. stolonifer and Penicillium spp. Its performance at 75–100% concentrations was statistically comparable to the synthetic fungicide Mancozeb, while the negative control (DMSO) showed no inhibition. The strong antifungal efficacy of CNSL is attributed to its phenolic constituents, particularly anacardic acids, cardanol, and cardol, which disrupt fungal cell membranes and suppress spore germination. This study concludes that CNSL is a promising natural biofungicide for managing yam rot pathogens. Its application could reduce postharvest losses, improve yam storability, enhance food security, and promote sustainable agriculture. Further research is recommended to develop safe, standardized CNSL formulations and evaluate their effectiveness under field and storage conditions.