Bacterial canker can infect twigs, branches, fruit, or the trunk. Elongate, dark, purplish cankers develop during early spring, often producing bacterial ooze in wet weather. The infected tissues often produce gum, although gumming is also caused by other factors. The cankers can girdle twigs and branches causing dieback. Leaves on girdled twigs typically yellow and fall by late summer. The bacteria typically infect via wounds caused by disease, insect damage, pruning, or frost injury. Infection can be spread by wind, rain, insects, pruning tools, or by planting or grafting with infected stock. The disease may spread throughout the entire tree (systemic infection) with or without visible symptoms.