Biological and Botanical Strategies for Managing Alternaria Leaf Spot Disease in Stevia rebaudiana (Bertoni)

The experiments were conducted research laboratory of Department of Biological Sciences, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj during 2023-2024. Observations were recorded at screening of plant leaf extracts and their antimicrobial activity against Alternaria alternata, assayed of secondary metabolites and active compound from the selected 10 botanicals. Results obtained that Azadirachta indica was significantly inhibited the mycelial growth of A. alternata over untreated control. The treatment T9 – A. indica was recorded least mean colony diameter at 15% concentration (9.53, 12.93, 21.51 and 23.71 mm), at 20% concentration (8.56, 11.31, 16.16 and 20.11 mm), at 25% concentration (8.06, 9.78, 10.78 and 13.28 mm) at 48hr, 72, hr, 96 hr and 120 hr after incubation respectively. While, A. indica at 15%, 20% and 25% concentration was found least radial growth and more % inhibition of A. alternata. Results summarized that A. indica was recorded minimum mycelial radial growth and maximum % inhibition as compared with all the botanicals leaf extract at 48, 72, 96 and 120 hrs after incubation.