High Desert Pests, Diseases, and Common Problems – Wetwood or Slime Flux

What Is Wetwood?

Wetwood, also known as bacterial wetwood, slime flux, or bacterial slime, is a bacterial disease that causes portions of the bark of its host tree to appear wet and ooze sap from the infected area. The sap is then infected by other pathogens to become slime flux.

Disease Cycle

Wetwood begins with an infection of a wound. The bacteria enter the xylem and block the transport of water which raises the internal pressure. This causes the accumulation of gas and liquids which in turn gives the bark a wet appearance. This wetwood is then followed up by sap that eventually oozes out from the inside as the pressure becomes too high.

Symptoms and Identification of Wetwood

For images of plants with wetwood scroll to the bottom for help in identifying if it is affecting your plant. If you have photos you’d like to add to the photos below you can send them to [email protected]

Management of Wetwood

There isn’t anything you can do to control wetwood or slime flux. This is a symptom of an earlier injury and should not be treated as a current problem. It can occur year after year, and there isn’t much you can do to stop it. Arborists used to put tubes in to help drain liquids inside the tree, but this is no longer practiced as it didn’t improve the problem and was opening the tree to other problems with an additional injury to place the tube.

Cultural Control

Make a concerted effort not to damage the tree unnecessarily through regular maintenance and other activities, especially around tree species that are susceptible to wetwood such as: elm, poplus, mulberry, and to a lesser extent sycamore, maple, willow and oak.

Chemical Control

There are no chemical treatments for slime flux or wetwood. If one is being sold it is a hoax and will not remove, prevent, or treat anything related to wetwood or slime flux. The only chemical of use is to occasionally spray a dilute solution of bleach on the slime to temporarily stop the fungi that colonize the sap once it oozes out to control the foul smell.

Below are some photos of wetwood and slime flux to help you diagnose your trees: