Data is lacking on the epidemiology of the disease. It has been observed that the pathogen is active between 10-20 deg;C and is limited by temperatures above 25deg C. Inoculation studies showed that the bacterium can infect the plant through natural apertures (stomata, lenticels) and wounds. Symptoms are usually expressed during spring and autumn when climatic conditions are favourable to the disease (cool temperatures, persistent rains, high humidity). It is suspected that the bacterium is spread by heavy rainfall, strong winds, animals and humans. Over long distances, trade of infected planting material can spread the disease