Potato is the only host that is naturally infected although the bacterium can colonized sugar beet roots without causing the disease. Other solanaceous crops such as tomato and eggplant have been successfully inoculated in the lab but the disease does not occur on these hosts in nature. While tubers most often become infected at or before planting, symptoms do not develop until after mid-season. The yellowing appears at the leaf margin. Interveinal mottling may occur followed by necrosis.
Symptoms progress up the plant until the entire stem becomes wilted and dies.
These symptoms may be less obvious when temperatures are cool. Another symptoms that is obvious on infected plants is the presence of the bacterium in infected vascular tissue. If an infected stem is cut crosswise and squeezed, a milky white ooze containing bacteria is extruded. One exception to the mid-season development rule is a symptom call early dwarf or green dwarf. This symptoms occurs on young Russet Burbank and Nooksack cultivars grown in the west.