Transmission: A. citrulli is mainly transmitted through seeds. In the field or transplant units, the bacterium can also be spread by water, in particular by overhead irrigation. Volunteer seedlings from infected seeds, buried infected rinds, and weed host plants can also act as inoculum sources. In US watermelon crops, it is now considered that the disease cycle usually begins with contaminated seeds which then result in infected seedlings. Overhead irrigation disperses the pathogen throughout transplant facilities and infected seedlings with inconspicuous lesions are transplanted to the field where the bacteria can spread to neighbouring plants. Diseased fruits often decay in the field and their seeds may then remain in the soil and eventually start a new disease cycle. Over long distances, trade of infected seed lots or transplants of Citrullus lanatus and Cucumis melo is probably the most important pathway for spreading the disease.
Pathway: Seeds, plants for planting, fruits of Citrullus lanatus and Cucumis melo.