Integrating Biological Fungicides into Cranberry Fruit Rot Management: Insights from Multi-Year Field Trials

Cranberry fruit rot (CFR) poses a major challenge in cranberry production due to the taxonomic diversity of fungi associated with it and increasing restrictions on the most commonly used broad-spectrum fungicides such as chlorothalonils and mancozeb, an ethylene bisdithiocarbamate (EBDC) fungicide. This study evaluated the efficacy of biological fungicides, particularly those containing Pseudomonas chlororaphis (Howler® and Esendo™) and Bacillus species (Serenade®Opti, LifeGard®, and Theia®), in managing CFR, across seven multi-year field trials conducted in Massachusetts from 2020 to 2023. Biological treatments were tested independently and in combination with chemical fungicides across multiple cranberry cultivars, with evaluations focused on CFR incidence, yield, and fruit quality. Results showed that Esendo™, containing P. chlororaphis and azoxystrobin, consistently reduced CFR incidence, achieving efficacy comparable to the grower-standard chemical treatment in specific application regimes. In contrast, solo applications of P. chlororaphis and Bacillus species generally provided limited efficacy, though their integration with chemical fungicides led to varied but often significant reductions in CFR. These findings suggest that biological fungicides can complement chemical treatments in integrated disease management (IDM), reducing chemical use, mitigating resistance risks, and promoting sustainability. The study highlights the potential of biological fungicides in cranberry fruit rot (CFR) management, supporting a shift toward sustainable cranberry production. Further research is needed to optimize application timing, dosage, and product combinations to ensure consistent efficacy in field conditions.