Management of seed-borne fungi in cowpea using leaf extracts and sodium bicarbonate

Abstract

The study investigated the in-vitro antifungal activities of sodium bicarbonate (NaHCO₃) and leaf extracts of Vernonia amydgalina (bitter leaf) and Azadirachta indica (neem) on fungal species isolated from two cowpea cultivars; IFE BROWN and Drum (a local cultivar). Concentrations of 1.95 mg/ml and 1.43 mg/ml were used for A. indica while 1.45 mg/ml and 1.15 mg/ml were used for V. amydgalina. Sodium bicarbonate was evaluated on all the isolates at 2.0 mg/ml and 3.0 mg/ml. The inhibitory effects of these antifungal agents were compared with benlate (a synthetic fungicide) on Potato Dextrose Agar. Benlate totally inhibited all the fungal isolates. Candida species isolated from the two cowpea cultivars were greatly inhibited by the antifungal agents while Trichoderma species isolated from IFE BROWN was the least inhibited. The inhibitory effects of NaHCO₃ and A. indica on Candida spp. were not significantly different and values ranged from 74.5% to 84%. The two concentrations of A. indica had better inhibitory effect on Pythium spp. than NaHCO₃. Vernonia amydgalina at 1.45 mg/ml inhibited A. niger and Candida spp. by 83.75% and 87.5% respectively while NaHCO₃ at 2.0 mg/ml inhibited Rhizopus stolonifer isolated from Drum by 75%. The study concludes that the two plant extracts and sodium bicarbonate had broad spectrum activities on fungal species and are therefore recommended as alternatives to toxic and synthetic fungicides.

Keywords: Cowpea, eco-friendly, fungicide, inhibition