In-vitro Evaluation of Bio Agents and Botanical Extracts against Alternaria alternata Causing Alternaria Blight of Dahlia

This study investigates the effectiveness of various bio-agents (Trichoderma viride and Trichoderma harzianum) and plant-based botanical extracts (neem, marigold, eucalyptus, ashwagandha, tulsi) in managing Alternaria alternata, a fungal pathogen responsible for Alternaria blight in Dahlia (Dahlia variabilis). The research was conducted using the poisoned food technique to assess the antifungal properties of these treatments at different concentrations (5%, 10%, 15%). In the case of botanicals Neem leaf extract showed the minimum growth a maximum inhibition (19.75 mm, 75.99%) and least were Tulsi leaf extract with maximum growth and minimum inhibition (61.60 mm, 25.13%) against A. alternata on the other hand Trichoderma viride showed the minimum growth a maximum inhibition (19.68 mm, 72.73%) and least were Trichoderma harzianum with maximum growth and minimum inhibition (24.51 mm, 66.03%) against A. alternata. Results indicate that both bioagents, particularly Trichoderma viride, and botanical extracts, especially neem and eucalyptus, significantly inhibited the mycelial growth of the pathogen. Mancozeb, a chemical fungicide used as a treated check, exhibited the highest inhibitory effect. These findings suggest that integrating bio-agents and botanicals could be an effective strategy for sustainable management of Alternaria blight in Dahlia cultivation.