Determination of Median Inhibitory Concentrations of Two Fungicides against fusarium Oxysporum F.sp. Vanillae Associated with Stem Rot Disease of vanillae

Two fungicides were evaluated for their in vitro effect on the colony growth of Fusarium oxysporumf.sp. vanillae, the causal agent of stem rot of vanillae after 48 hrs and 144 hrs of inoculation in pre-amended Potato dextrose agar (PDA) medium. The fungicides showed variable response in inhibiting the growth of the pathogen according to their nature and specificity at different inhibitory concentrations of Tricyclazole (Beam 75% WP) and Matco (Metalaxyl 8 %WP Mancozeb 64% WP). The maximum per cent inhibition on growth of Fusarium oxysporum f.sp. vanillae by Tricyclazole was high at concentration of 800 ppm 79.99 per cent at 48 hrs, 90.99 per cent at 144 hrs of incubation. The Matco fungicide showed 79.87 per cent inhibition at 800 ppm concentration at 48 hrs and inhibition was 90.78 per cent at 144 hrs post treatment. Interestingly, the toxicity of Tricyclazole was found to increase with time intervals from 24 hrs (IC50 value=589.9 ppm) till 144 hrs (IC50 value=107.1 ppm). The toxicity of fungicide Matco was also found to increase over time from 24 hrs (IC50 value=575.2 ppm) to 144 hrs (IC50 value=33.00 ppm) post treatment against Fusarium oxysporum f.sp. vanillae.