Spotless strawberry plants: how to keep them free from Xanthomonas?

Xanthomonas fragariae (Xfr) is the causative agent of angular leaf spot of strawberry, a quarantine organism in Europe in plant propagation material (EPPO A2). Protected cultivation of strawberry plants in general resuIts in a pathogen free crop. However, if plants are grown in the field, infections occasionally occur which can result in high economic damage. Motile Xfr cells can enter the plants via wound or natural openings, in particular via stomata. The development of symptoms is favored by a high relative humidity and when temperatures are between 18-24 degrees Celsius. Under high-moisture conditions, bacteria can exude from lesions and provide secondary inoculum which can be dispersed in different ways.