Antifungal Activity of Some Botanical Oils Against Alternaria solani, Causing Leaf Blight of Potato

The inhibitory effects of five botanical oils (Neem, Citronella, Pine, Clove and Garlic) at 0.05%, 0.1% and 0.15% concentrations along with sole application of solvent Xylene were tested under in vitro condition. Four isolates (A₁, A₂, A₃ and A₄) of Alternaria solani were collected from different potato growing areas of West Bengal, India. Significant antifungal activities of these five botanical oils against four isolates of A. solani were noticed. Garlic (0.15%) inhibited the maximum mycelial growth of A₁ (90.3%). Spore germination was also inhibited due to application of garlic (0.15%) in case of all the isolates of A. solani. Out of five botanical oils, garlic (0.15%) exhibited maximum inhibition of mycelial growth and spore germination over control including sole application of solvent, xylene. Field studies also reveal that foliar sprays of garlic oil (0.15%) not only suppressed the Alternaria leaf blight infection but also enhanced the total tuber yield. Hence, botanical oils should be used as non hazardous natural fungicides in controlling plant pathogenic fungi.