Compatibility of Indigenous Trichoderma spp. with Selected Fungicides and Insecticides

Aims: Evaluation of compatibility of indigenous Trichoderma isolates obtained from different agro ecological units of Kasaragod district, Kerala, India, with commonly used soil fungicides and insecticides. Study Design: CRD. Place and Duration of Study: Department of Plant Pathology, College of Agriculture Padannakkad, between November 2022 and November 2023. Methodology: Purposive sampling surveys were conducted in eighteen different locations within the agro ecological units viz., AEU 2 (Northern coastal plain), AEU 7 (Kaipad lands), AEU 11 (Northern laterites), AEU 13 (Northern foot hills) and AEU 15 (Northern high hills) of Kasaragod district, Kerala, India. Native Trichoderma species were isolated in Trichoderma Selective Medium (TSM) by using dilution plate technique. The compatibility of promising indigenous Trichoderma isolates with commonly used fungicides at recommended concentrations viz., copper hydroxide (0.15%), mancozeb (0.3%), carbendazim (0.2%), hexaconazole (0.2%) and metalaxyl (0.1%); and insecticides viz., chlorpyriphos (0.06%) and carbosulfan (0.05%) was evaluated using poisoned food technique. Statistical analysis of the results obtained was carried out. Results: At the lowest tested concentration of copper hydroxide (0.1%), isolates Tr 37, Tr 52, and Tr 55 demonstrated complete compatibility, without any growth inhibition. Isolates, Tr 5, Tr 12, Tr 37, Tr 40, and Tr 41 were highly susceptible to mancozeb, displaying 100% inhibition at all tested concentrations. Carbendazim was found inhibitory for all isolates at every concentration tested, resulting in complete growth inhibition. Hexaconazole showed a high level of inhibition, with inhibition rates exceeding 70% across all tested concentrations. Metalaxyl significantly suppressed radial growth across all concentrations, though isolates, Tr 37, Tr 52, and Tr 55 exhibited relatively low inhibition regardless of the concentration. The Trichoderma isolates were found relatively more compatible with insecticides chlorpyriphos and carbosulfan. Conclusion: T. harzianum isolates exhibited a higher sensitivity to fungicides tested. T. koningiopsis isolates demonstrated relatively higher compatibility with all tested fungicides but were found to be affected by insecticides. All the isolates were found relatively more compatible with insecticides chlorpyriphos and carbosulfan.