Disease of Trees
Charles H. Hadden, Professor Emeritus
Alan S. Windham, Professor
Entomology and Plant Pathology
George M. Hopper, Professor
Wayne K. Clatterbuck, Associate Professor
Forestry, Wildlife & Fisheries
Wetwood is a water-soaked condition of wood in the
trunk and branches of trees. This condition has been attrib-
uted to bacterial infection in the inner sapwood and outer
heartwood area of the tree. Infection is normally associated
with wounding or environmental stress on the tree. The
bacteria, Enterobactor cloacae, has been implicated as the
cause of wetwood in elm, but numerous other bacteria have
been associated with this condition in other trees such as
cottonwood, willow, ash, maple, birch, hickory, beech, oak,
sycamore, cherry and yellow-poplar. Bacteria alter wood
cell walls, causing moisture content of the wood to increase.
Infected wood may also have a high (basic) pH and a high
concentration of microelements.
The most common evidence of wetwood is bleeding
or “fluxing” of sap from the trunk or larger limbs of a tree.
Often this fluxing is associated with a wound, but has also
been observed where no obvious wound existed. Bacteria
associated with wetwood are common in soil and water
Stain associated with bacterial wetwood disease on the trunk
of pin oak.
Closeup of damage to bole (pruning scar) where fl ux of sap
is exuding. Notice the bird peck hole where birds are either
hunting for insects attracted by the fl ow of sap or actually
feeding on the sap.
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