Slime Flux and Bacterial Wetwood - Wetwood or Slime Flux Disease

Russell Friesen

Poplar, elm, birch, maple, apple and mountain ash can all develop a condition known as bacterial wetwood. Often bacterial wetwood symtoms involve a liquid that oozes and bubbles through bark cracks and wounds from birds, nail holes, and pruning. The oozing liquid is known as slime flux, a name inspired by the slimy, smelly, brown appearance of the liquid.

Description

The bacterial wetwood is found in the roots, branches, and trunks. The cause of the condition is an infection of the heartwood caused by several common types of anaerobic soil bacteria (bacteria to which oxygen is toxic). These bacteria feed on substances in the wood, releasing fatty acids, methane and carbon dioxide gases. The fatty acids go rancid leaving the wood of the tree water soaked and foul smelling.

The gaseous by-products create a hydraulic pressure which forces liquids out of cracks in the bark, branch crotches and pruning wounds. These fluids will turn brown once they come in contact with air, and leave a slimy, fetid ooze dripping down the bark. The liquid raises the pH of the tree making the interior more alkaline. The bacteria do not cause any wood decay, and infected wood is also very resistant to decay. It has been observed that elm stumps with wet wood, are protected from decay for at least three years.

Infection is thought to enter the tree primarily through root uptake, but contaminated pruning tools have also been reported to transmit the condition (but not in elm trees). Wood boring insects such as the native elm bark beetle have also been reported to transmit the disease. Of course if you have elm bark beetles in your tree, bacterial wetwood is the least of your problems; Dutch Elm Disease should be your primary concern.

University of Saskatchewan College of Agricultural Bioresources