Biocontrol efficacy of endophytic Trichoderma spp. in fresh and dry powder formulations in controlling northern corn leaf blight in sweet corn

Seventy-three endophytic Trichoderma spp. obtained from healthy corn leaves collected in the central and northeast parts of Thailand were evaluated for their biocontrol activity against northern leaf blight disease due to Exserohilum turcicum. Among them, T. asperellum KUFA0702, KUFA0703, T. hamatum KUFA0706, T. harzianum KUFA0710, and T. harzianum KUFA0713 showed promising biocontrol efficacy against the disease under laboratory and greenhouse conditions; thus, they were selected for control efficacy evaluation under field conditions using their fresh and dry powder formulations. The results found that the fresh formulation of each Trichoderma strain displayed better biocontrol effects than their dry formulation. In field trials, the application of fresh formulation of T. harzianum KUFA0710 displayed the best disease reduction at 55.70%, while its dry formulation caused 47.46% disease reduction followed by T. harzianum KUFA0713 at 49.92% and 43.84% disease reduction when applied as fresh and dry formulations, respectively. The antagonistic activities of Trichoderma spp. included fast growth with high competition for space and nutrients and production of antifungal crude extracts. Moreover, all Trichoderma strains showed compatibility fungicides at recommendation rate with azoxystrobin (1000 ppm) and difenoconazole + azoxystrobin (500 ppm). These fungi can serve as alternative fungicides or be combined with fungicides for integrated pest management.