Microbiology Research Journal International

Spot blotch caused by Bipolaris sorokiniana is one of the major constraints limiting barley (Hordeum vulgare L.) production worldwide. The present study evaluated the antifungal efficacy of eight botanical extracts against B. sorokiniana under laboratory and field conditions to identify eco-friendly alternatives for disease management. In vitro evaluation was conducted using the poisoned food technique by incorporating aqueous extracts of garlic (Allium sativum), eucalyptus (Eucalyptus globulus), neem (Azadirachta indica), black cumin (Nigella sativa), onion (Allium cepa), ginger (Zingiber officinale), Jacaranda mimosifolia and Thevetia peruviana into potato dextrose agar at 2, 5 and 10% concentrations. Based on laboratory performance, the extracts were further evaluated under field conditions during the rabi season of 2024-25 in a randomised block design. Antifungal activity increased with increasing extract concentration. Garlic extract exhibited the highest efficacy by completely inhibiting mycelial growth (100%) at a 10% concentration, followed by eucalyptus (78.43%) and J. mimosifolia (73.20%). Under field conditions, garlic significantly reduced spot blotch severity and recorded the highest grain yield (28.20 q/ha), representing a 22.61% increase over the untreated control. Eucalyptus (27.80 q/ha), J. mimosifolia (27.60 q/ha), neem (27.40 q/ha) and T. peruviana (27.00 q/ha) also effectively suppressed disease and improved yield. The findings demonstrate that garlic, followed by eucalyptus and J. mimosifolia, possesses strong antifungal potential against B. sorokiniana and can serve as environmentally sustainable alternatives to synthetic fungicides for the integrated management of barley spot blotch.