Pectinolytic bacteria of the family Enterobacteriaceae, specifically Dickeya solani, are known to cause potato blackleg. This study aimed to evaluate the effectiveness of a mixture of two bacteriophages from the genus Limestonevirus in controlling Dickeya solani in both greenhouse and field trials. The potential of bacteriophages for ecological potato control was also assessed. The phages φDs3CZ and φDs20CZ were isolated from soil in the Czech Republic between 2019 and 2021. They were applied preventively and curatively as a solution on artificially wounded and inoculated seed tubers immediately prior to planting. The phage-treated variant showed a highly significant reduction in the extent of D. solani infection compared to the untreated control in both the greenhouse and field trial. The effect of the phages depended on the concentration of the solution, the rate of tuber injury, and the sequence of application. When applied preventively, the phages caused a significantly higher reduction in the rate of blackleg symptoms (86.7% and/or 87.1%) compared to the curative application (54.6 and/or 36.6%). Phages φDs3CZ and φDs20CZ showed potential for use in biological potato control against Dickeya solani.

The pectinolytic Dickeya solani bacterium is an important pathogen found in potatoes. We conducted laboratory and field experiments mimicking severe and mild Dickeya spp. infection and investigated the application of a mixture of two lytic bacteriophages before and after bacterial infection to protect the plants. Application of the phage solution to tuber disks and wounded tubers did not completely eliminate the infection but reduced the development of soft rot symptoms by 59.5–91.4%, depending on the phage concentration. In the field trial, plants treated with bacteriophages after severe Dickeya infection had 5–33% greater leaf cover and 4–16% greater tuber yield compared to untreated plants. When simulating a mild infection, leaf cover was 11–42% greater, and tuber yield was 25–31% greater compared to untreated plants. We conclude that the phage mixture has the potential to protect potatoes ecologically from D. solani.