Bacterial canker and blast—Pseudomonas syringae
Cankers are irregularly shaped, brown, water-soaked areas that develop in the bark and outer sapwood
of spurs, branches, and the tree trunk. Small cankers can develop on twigs at the base of infected buds.
In the spring, amber-colored gum may exude from the margins of cankers. In cold, wet weather, blossoms
may turn brown, shrivel, and cling to the tree. Leaves also may develop dark spots that later drop out.
Sunken spots may develop on young fruit.
Avoid planting on shallow soils. Where feasible, delay pruning until late winter. Cauterize pruned branches
with a hand-held propane burner in areas where Eutypa or bacterial canker are a concern. If trees have
been infected, remove entire affected branches in the summer, being sure to eliminate the entire canker
and a few inches below. Choice of rootstock and varieties can influence the susceptibility of plums, prunes,
and cherries to bacterial canker and blast. Fall or spring foliar applications of complete micronutrients
(especially zinc and boron) may help prevent bacterial canker, as nutrient
deficiencies make all stone
fruits, especially cherries, more susceptible. Trees stressed by nematodes are more likely to be severely
damaged. Check with a local advisor for the best recommendations.
Gumming on branches