They can also be spread from plant debris by wind, rain and irrigation water. The bacteria may reside on the surface of bean leaves as epiphytes without causing disease, or may incite lesions under favorable environmental conditions. This primary inoculum can then be easily spread by wind and water into nearby bean fields, often resulting in subsequent disease outbreaks during favorable conditions. The incidence and severity of bacterial diseases are affected greatly by environmental, host and cultural factors. Typically these pathogens most commonly infect young foliage and symptoms are rarely seen on older leaves.
Symptoms usually appear on older leaves, even at low humidity.
Violent storms with hail and high winds cause plant wounding which enable pathogens to enter and infect plant tissues. Wounds caused by damaging plants with farm machinery or field workers during cultivation can spread pathogens, especially when foliage is wet. Initial halo blight symptoms. Foliar halo blight symptoms. Young brown spot lesions.