Sappy bark—Trametes versicolor
Sappy bark, also called papery bark, is a minor fungal disease of apple that occurs on older trees in
most growing areas. The sappy bark fungus enters limbs and larger branches at pruning cuts. Infected
bark and wood tissues decay, becoming spongy and discolored. Affected bark frequently peels away, exposing
decayed tissue beneath. During damp weather, affected bark appears spongy; when it is dry it looks papery.
Dark sap sometimes oozes from diseased areas. Bracketlike, spore-producing structures may form along
the edges of affected areas. Sappy bark cankers can girdle branches, or if infections are located on
the trunk, they can girdle and kill the tree.
To reduce the incidence of sappy bark, maintain your trees in good vigor and always make pruning cuts
flush with the limb. Leave no stubs when pruning; these can be invaded by the fungus. If diseased bark
and wood are present in the tree, cut them away and destroy.