Efficacy of Botanicals as Biocontrol Agents Against Leaf Spot and Blossom Blight Pathogen of Marigold: A First Report from Longleng District of Nagaland, India

Aims: To study about etiology and organic disease management strategies of Fusarium oxysporum induced blossom blight in marigold (Tagetes spp.), cultivated in and around Longleng district of Nagaland. The experiment aimed to formulate an effective organic disease management module to combat the disease and assess the efficacy of plant extracts and biocontrol agents in suppressing fungal growth. Study Design: A completely randomized design (CRD) was employed for laboratory-based trials, and an exploratory survey was conducted during the winter season of 2024 to monitor disease incidence in marigold-growing areas around Longleng district of Nagaland. Place and Duration of Study: Field survey has been carried out in Longleng district of Nagaland. All the laboratory works has been carried out in laboratory of Assam Agricultural University(AAU), Jorhat, Assam. Duration of research is 6 months. Methodology: The tested phytoextracts at 10% and 20% concentrations included leaves of neem (Azadirachta indica), tulsi (Ocimum sanctum), garlic (Allium sativum), and other local plant species. Biocontrol agents such as Trichoderma viride, Trichoderma harzianum, and Pseudomonas fluorescens were collected from the rhizosperic soil of Marigold as well as from local fields and research institutions for evaluation. Disease incidence and severity were measured based on Percent Disease Intensity (PDI). Results: The study demonstrated that garlic extract, at both tested concentrations, achieved complete inhibition (100%) of fungal growth. Additionally, several other plant extracts exhibited notable antifungal properties. Among the biocontrol agents, Pseudomonas fluorescens showed a strong antagonistic effect against Fusarium oxysporum (82.65%). These findings underscore the potential for incorporating phytoextracts and biocontrol agents into effective organic disease management strategies for marigold cultivation. Conclusion: From the study, it is recommended to optimize the application of garlic extract, exploring its effectiveness in field conditions, and evaluating its potential in combination with other biocontrol agents or plant extracts.