ASHS 2025 Conference

Eastern redbuds (Cercis canadensis), valued for their vibrant flowers and heart-shaped foliage, are economically important trees in Tennessee nurseries. However, large-scale production is challenged by fungal canker pathogens that compromise tree health and marketability. In 2023, field and container-grown eastern redbuds in Tennessee exhibited dieback, dark, sunken necrotic lesions, and vascular discoloration. Fungal isolates from diseased tissue exhibited morphological and microscopic characteristics consistent with members of the Botryosphaeriaceae family. Molecular identification was done by amplifying the ribosomal internal transcribed spacer (ITS), β-tubulin (TUB), and translation elongation factor (EF1-α) gene markers. The phylogenetic analysis of concatenated ITS, TUB, and EF1-α sequences confirmed the pathogen as B. dothidea, and the pathogenicity test further established its pathogenic nature. Currently, there is no effective strategy for managing Botryosphaeria canker in redbuds. This study aimed to identify the causal agent and assess the efficacy of fungicides and biofungicides for canker disease management. Greenhouse trials were conducted from May to November in 2023 (Trial 1) and 2024 (Trial 2) using a completely randomized design with 14 treatments, which included non-treated, inoculated control, non-treated, non-inoculated control, and wound control, with six replications per treatment. Treatments included chemical fungicides (Avelyo, Pillar SC_LR, Pillar SC_HR, Postiva, SP2700WP, SP2478, and Kleengrow) and biofungicides (BotryStop WP, RootShield PLUS, Stargus, and Tril-21). These treatments were applied as foliar spray, wound treatment, drench, or sprench at 14-day intervals. One-year-old container-grown healthy eastern redbuds were wounded and artificially inoculated with fungal mycelial plugs, followed by fungicide applications. Disease progression was monitored over a six-month period by measuring plant height, width, lesion length, and pathogen recovery. All tested fungicides and biofungicides significantly reduced canker lesion length and pathogen recovery compared to the non-treated, inoculated controls. The most effective treatments in reducing Botryosphaeria canker severity were BotryStop WP (Ulocladium oudemansii strain U3), RootShield PLUS (Trichoderma harzianum T. virens G-41), and Pillar SC (triticonazole pyraclostrobin). However, no significant difference was observed in plant height and width among different treatments. These findings provide nursery growers with an idea of the causal agent and effective management strategies for reducing the severity of Botryosphaeria canker in redbud production.