Common bacterial blight caused by Xanthomonas campestris pv. phaseoli is a very important disease of field bean in many regions of the world and can lead to high losses of production (25 to 60%). The bacterium is primarily transmitted through infected seed. Xanthomonas can survive over 15 years in seed before emerging to infect the plant during the vegetative period. The disease occurs on all above-ground tissues from which bacteria can be spread by humans, farm implements, insects, wind, rain or hail.