In Planta Application and Efficacy of FireFighter-A Phage Cocktail for Combating Fire Blight

Fire blight, caused by Erwinia amylovora, poses a significant threat to Rosaceae crops and has caused substantial damage to South Korea since its emergence in 2015. Traditional control methods, including antibiotic- and copper-based treatments, have shown limitations, underscoring the necessity for alternative solutions to enhance efficacy while addressing the concerns associated with antibiotics. This study evaluated the efficacy of FireFighter-A, a novel phage cocktail, in managing fire blight. Comprising four phages-Fifi318, Fifi451, pEa_27, and pEa_47-FireFighter-A demonstrates a broad host range that covers all recent isolates against E. amylovora and E. pyrifoliae, along with high stability under various conditions, including temperature, pH, and buffers. Trials with immature apple fruits, tissue culture rootstock plantlets, acclimated M26 rootstock plantlets, and blossoms have demonstrated that FireFighter-A provides superior biocontrol efficacy through synergistic effects, outperforming individual phages. Moreover, it significantly reduced fire blight symptoms and infection rates with a performance comparable to or exceeding that of streptomycin. These findings support the use of FireFighter-A as an effective and environment-friendly alternative for fire blight control.