Efficacy of two biofungicides for early blight field management in potato (Solanum tuberosum L.)

Abstract

The objectives of the work were I) to establish the compatibility between Trichoderma asperellum Samuels et al. and Pseudomonas protegens Ramette et al. under laboratory conditions and II) to determine the efficacy of the biological products based on both organisms in controlling early blight. For the study in the field during two campaigns, plots of 27 m² were used in a non-randomized block design. Compatibility of both products was determined in the laboratory. In the field, eleven treatments were used in the first campaign, and the best ones were selected for being applied in the next campaign. In the treatments to the soil, a conidial suspension of T. asperellum strain Ta. 85 at a concentration of 7x10⁷ CFU were applied to the soil at a rate of 8 L per treatment. In the first campaign, once the symptoms of the disease were detected, the aforementioned biofungicides, at the respective concentration of 7x10⁷ CFU.ml^-1 and 10⁸ CFU.ml^-1, were applied to the foliage at a rate of 8 L per treatment. In the second campaign, the biofungicides were applied to the foliage when the symptoms were detected and 15 days later. There was compatibility between the biological products, indicating that both can be applied together in the biological control of early blight. The treatments with T. asperellum to the soil plus the tubers plus the combination of T. asperellum and P. protegens with double applications to the foliage and T. asperellum to the soil plus the tuber plus double application of Pseudomonas to the foliage were significantly effective in reducing the disease, respecting to the control, where the latter treatment stood out. These results suggest that these products could be promising for the biological control of this pathogen in the potato crop under field conditions.