| Bacterial wetwood, also known as slime flux, is
caused by an infection of one or more of several
bacteria. It results in a water-soaked, oozing or
bleeding condition of wood, which occurs in the
trunk, branches and roots of shade and ornamental
trees. It is normally not serious in most trees but is a
chronic disease, which causes concern and can
contribute to a general decline in tree vigor over
time. Trees most susceptible to the disease include:
elms, apple, crabapple, London plane, redbud,
aspen, dogwood, magnolia, Russian olive, beech, fir,
maple, sour gum, birches, hemlock, mountain ash,
sycamore, boxelder, hickory, mulberry, sweet gum,
butternut, horse chestnut, oaks, tulip tree,
cottonwood, linden, pines, black locust, poplar,
willow and walnut.
Symptoms and Diagnosis
Symptoms vary with geographical location
suggesting that the environment influences disease
development. Trees in the western United States
show more variability in internal disease
development with much less bleeding and symptom
expression than trees in the East and Midwest.
Wetwood appears internally in the trunk and large
limbs as a dark brown-black water-soaked area
when the area is sectioned. The first external sign of
wetwood is usually bubbling and seepage from
wounded tissue in V-shaped branch crotches,
wounds made by removal of branches, injection
holes and trunk cracks. Insects are often attracted to
the ooze on which they feed but there is not any
evidence that these insects cause damage or
transmit the bacteria but it is believed that some
wood boring insects such as beetles may transmit
the disease.
Life Cycle
Organisms, most commonly bacteria, infect the tree
deep in the tissue and start a process of
fermentation. The resulting pressure (up to 60 psi)
forces the bacterial ooze out cracks, branch stubs
and pruning cuts. This ooze discolors bark, kills the
cambium near the cut preventing proper callusing of
wounds and kills grass and other plants on which it
drips. Bacterial wetwood is noticed externally when
it exudes slime and leaves a stain on the bark.
Wilting of foliage is common in young trees; old
trees are more likely to develop a general decline in
vigor or branch dieback in the upper crown.
Integrated Pest Management Strategies
1. There is no cure or preventive treatment to avoid
infection and development of bacterial wetwood.
The following strategies may help.
2. Fertilization. Fertilize stressed trees to stimulate
vigorous growth and lessen the severity of the
disease but refrain from over fertilizing healthy
vigorous trees as this may increase their
susceptibility to the disorder.
3. Drainage tube. Inserting tubing into the draining
area will make the problem more cosmetically
pleasing but will not help cure the disease and
may actually lead to greater problems in the
future. By causing a deeper wound through
inserting the tube you may be spreading the
disease deeper into the tree. Drain tubes can,
however, help release pressure where it is known
that the wetwood is confined to the inner core of
the tree. The tube will, however, allow oxygen into
the tree’s inner core, which can promote wood
decay. In summary, installing drainage tubes may
cause more problems than doing nothing.
4. Pruning. Disinfect tools with 70% rubbing
alcohol before pruning a tree. Remove dead and
weak branches. Promptly prune and shape bark
wounds. Remove diseased bark and underlying
wood around infected cuts and apply a
disinfectant coat of shellac. Additional coating of
a wound dressing is an option primarily for a
cosmetic effect. |
