Spread of Xanthomonas fragariae in strawberry fields by machinery

The spread of Xanthomonas fragariae in a strawberry field by mowing and runner cutting machinery was studied in the Netherlands during autumn. The blades of a rotary mower became heavily contaminated after trimming the leaves of symptomatic plants. Use of a contaminated mower resulted in infection of plants that were initially free of X. fragariae, even at a distance of 4 m (i.e. 10 mother plants) from the symptomatic plants. Directly after mowing,the pathogen could be detected on damaged leaves at a density of 103–105 cells g-1.Infections were established, although 3 months after mowing symptoms were still absent. There were indications that the use of the mower resulted in the spread of infected leaf material from symptomatic plants to neighbouring beds. Spread by a runner cutting machine was also studied. Again, after cutting the runners of symptomatic plants, high numbers of X. fragariae cells were recovered from debris on the discs of the machine. During cutting, the cut ends of runners of plants initially free of X. fragariae became contaminated, even ata distance of 4 m from the symptomatic plants, but only at low densities of 103 cfu g-1. Three months after stolon cutting, infections were detected in some of the cut plants.