Bacterial Wetwood (Slime Flux) in Trees

It is the time of the year when wetwood or slime flux might be observed on infected trees. A unique feature of the disease includes a water-soaked, yellow-brown discolored area along the bark. A foul-smelling liquid (slime) oozes out of bark cracks and wounds and results in the build-up of dry scum. This condition is common in poplar and elm but can also be found in maple, birch, oak, sycamore, ash, linden, redbud, fir, beech, willow, cherry, plum, butternut, walnut, hickory, apple, cottonwood, aspen, and mulberry.

Bacteria enter through open wounds from boring insects, mechanical damage, or poor pruning. The build-up of bacterial populations within the tree causes fermentation of tissues resulting in internal gas pressure of up to sixty pounds per square inch. Foul-smelling, slimy liquid then exudes out of bark cracks. Most of these cracks appear during the winter months possibly due to the inability of affected wood tissues to withstand temperature fluctuations. Infection may result in heartwood decay or degradation of bark tissues and in some cases (e.g., elm trees) wetwood liquid may be translocated to the upper crown and may result in wilting and branch dieback.

There is no known effective control for slime flux. Inserting drain tubes around the affected area is no longer recommended. It may only help spread bacterial population within the tree and create wounds conducive to the entry of wood decaying fungi. Preventative measures such as avoiding moisture stress, proper pruning and adequate fertilization may help invigorate trees. Do not disturb soil around base of tree to prevent wounds through which bacteria can enter.

This article originally appeared in the April 23, 1999 issue, p. 45.


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