Endophytic Trichoderma and Bacillus isolates suppress Lasiodiplodia theobromae-associated dieback in blueberry under arid coastal conditions

Blueberry (Vaccinium corymbosum L.) production represents one of the main pillars of Peruvian agro-exports; however, its sustainability is increasingly threatened by wood-infecting fungal diseases such as dieback. This study was conducted in the Nuevo Proyecto-Olmos area (Lambayeque, Peru), covering a total cultivated area of 176 ha. The objectives were to molecularly identify the fungal pathogens associated with blueberry dieback to perform a preliminary evaluation of the antagonistic potential of endophytic microorganisms. Pathogens were isolated and characterized using morphological and molecular approaches, followed by pathogenicity tests and in vitro efficacy assays of beneficial microorganisms. Disease incidence was dominated by Lasiodiplodia spp., followed by Neopestalotiopsis, Fusarium, and Diaporthe. Lasiodiplodia theobromae was the most prevalent and aggressive species, confirming its association with the observed disease symptoms. For the genus Lasiodiplodia, temperatures between 25 and 30 °C favored mycelial growth, whereas 20 °C and 35 °C limited development. Endophytic isolates of Trichoderma spp. and Bacillus spp. inhibited pathogen mycelial growth by more than 60% under in vitro conditions. These findings highlight the potential of beneficial microorganisms as preliminary candidates for the biological control of wood-infecting fungi in blueberry production systems.