ASHS 2024 Conference

Entomopathogenic fungi offer an alternative strategy for citrus growers seeking environmentally friendly pest management solutions. This study aimed to assess the ability of a commercial strain of the fungus Beauveria bassiana to become endophytic in citrus plants after a single foliar application. A completely randomized block design, consisting of ‘Valencia’ sweet orange trees (Citrus × sinensis) grafted on ‘US-942’ (Citrus reticulata × Poncirus trifoliata) rootstock, was established under greenhouse conditions. Treatments comprised 6 replications of treated plants in two separate greenhouses (n = 16 per greenhouse), along with one control (water only). Treated plants were foliar sprayed asynchronously with the fungus at the beginning of each experimental trial per treatment. To assess endophytism over time, a series of cohorts were destructively sampled every two months. Spore deposition was assessed using cover slips post-spray application of all treatments. Additionally, detached leaves collected post-spray were imprinted on potato dextrose agar (PDA), amended with dodine and bactericides, to determine spore coverage of the leaf surface by counting colony forming units. To assess endophytism, sterile samples of plant organs (i.e., leaves, stems, and roots) were placed onto PDA-dodine plates to allow detection of phenotypic mycelia. Results from the first cohorts indicated successful application of the fungi on the citrus leaves, and endophytism was assessed after two months. Additionally, no statistically significant changes were recorded in terms of plant height, root, stem, and leaf biomass, as well as stem girth. This project contributed to a clearer understanding of the long-term endophytic persistence of commercially available entomopathogenic fungi and their effect on plant growth in citrus trees. The trial will continue in the field for additional screening.