Are your trees weeping along the bark? A possible cause is a non-decaying, bacterial disease called "Wetwood". The disease occurs in the inner wood of many types of trees, including maple, mulberry, poplar and willow. It is most common on elms. It's seldom fatal; in fact, most affected trees live to a ripe old age.

The most noticeable symptom of bacterial wetwood is liquid weeping from openings in the tree bark. This liquid ooze is known as "Slime Flux". During warm weather, the bacterial activity increases, resulting in increased gas pressure, which forces moisture out cracks, wounds or branch crotches. Flux activity may start and stop from time to time. The liquid "flux" turns dark on exposure to air, and may be foamy, or have an unpleasant odor. As it runs down the trunk, it dries to a white-gray color, which is often seen as light discolored strips running down the tree trunk. The flux is toxic enough to kill grass at the base of the tree, and prevent callus formation, which is necessary for wound healing.

There is no chemical that stops or controls wetwood. The first line of defense against bacterial wetwood is to avoiding unnecessary wounding. Cultural practices to keep the tree growing well and free from unnecessary stress, may also help. This would include aerating the lawn area around trees, spring fertilization and watering during dry spells.

In the past, drain tubes were installed, to remove excess liquid, and lower internal pressures. This may help stop the spread of bacteria throughout the tree. However, it is now felt that the additional wounds increase entrance of wood decay fungi, which may be more damaging to the tree than the wetwood infection.

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