Perennial canker of stone fruit
Disease
Perennial canker of stone fruit
Leucostoma cincta (Fr.:Fr.) Höhn Leucostoma persoonii Höhn.
Distribution: Widespread; but most damaging in cooler climates such as the northeastern US and Canada.
Photos
Cankers are elliptical, exude amber gum and form concentric rings from the yearly alternation of callus formation and tissue invasion.
Wayne Wilcox, Cornell Univ.
C
Small twig infections are usually found around winter-killed buds, leaf scars, and picking and pruning injuries. They appear as sunken discolored areas with alternating zonation lines and may ooze amber gum unless the twig is killed. On infected branches, the leaves often turn yellow, wilt and die (A). Dead twigs, branches, and canker margins become covered with pinhead-sized black pimples (pycnidia) that break through the bark (B). Pycnidia exude flesh- to orange-colored tendrils of spores under wet conditions. Main trunk and branch infections usually start at pruning wounds or winter-killed tissue. Cankers are elliptical and exude excessive amounts of amber-colored gum. Cankers often develop a series of concentric callus rings, reflecting the yearly alternation of callus formation and tissue invasion (C).