Bacterial canker—Pseudomonas syringae
Symptoms of bacterial canker are most obvious in spring and include limb dieback with rough cankers
and amber-colored gum. There may also be leaf spot and blast of young flowers and shoots. A more severe
of the disease, the sour sap phase, generally occurs in younger trees. This phase may not show gum and
cankers, but the inner bark is brown, fermented, and sour smelling. Reddish flecks and pockets of bacterial
invasion in bark occur outside canker margins. Trees frequently sucker from near ground level. Cankers
do not extend below ground.
Identification | Life cycle
Avoid planting on shallow soils. Plant less susceptible
rootstocks. Generally, vigorous trees have less trouble with
bacterial canker. Practice measures, such as adequate fertilizer and irrigation, that encourage good plant growth. Prune severely
cankered or dead scaffold limbs to discourage secondary invasion
by wood rot organisms.