What is the oozing, foul smelling liquid coming out of my tree’s trunk?
Image Citation (Photo 1): Joseph O'Brien, USDA Forest Service, Bugwood.org
One of the main diagnoses of this would be Wet Wood -Enterobacter nimipressuralis -often called, Flux or Slime Flux. Flux is a slimy, oozy liquid, that more often then, not also has an offensive smell. It drips or “oozes” from tree trunks, crotches, cracks and branch crotches. It is most often seen on Oak, Elm, Birch, and Maple trees. This sap is more prevalent during Spring and Summer while the tree is actively growing. This sap/flux often attracts insects, contrary to many beliefs the insects are not the cause of the Flux they appear after the flux comes out.
Many different bacterial infections can lead to Flux. Most often these infections begin in the Heartwood or Sapwood of trees and are caused by soil inhabiting bacteria. Wet Wood causing bacteria can grow anaerobically (without oxygen) in internal tissue of wood. These infections on the inside of the trees structure lead to increased pressure on the vascular system. The pressure causes the excess fluid (sap/flux) to ooze out of any opening it can find, usually crotches, cracks in the bark, or even old wounds. When the flux/sap oozes out it leaves behind a White or Grey streak on the bark or branches or the tree.
Image Citation (Photo 2): Rebekah D. Wallace, University of Georgia, Bugwood.org
Flux/Wet Wood infected trees have internal wood that is wet but not necessarily decayed. The infected portions of the tree will also have a higher pH level then the rest of the tree. Wet Wood infection actually prevents decay from fungi. The spread of Wet Wood/Flux within a tree is limited by the trees natural defenses. Trees have a natural ability to heal themselves often times human interference can cause more harm then, good, this is very true with this type of infection!
There is no specific treatment for Wet Wood/Flux. It is important with any tree that is stressed to make sure you are properly watering (definitely not overwatering) and if necessary, fertilizing. Some recommend removing dead or loose bark in the area of the wound to help keep the area dry. Others suggest creating a drain to allow the flux to ooze onto the ground instead of the bark of the tree, this also helps keep the area dry. It is recommend to NOT prune healthy branches on an infected tree as open wounds can lead to the spread within the tree itself. Deep fertilizing injections can also create new wounds and lead to spreading of the infection. Wet Wood does usually spread into new wounds and injuries so be careful around infected trees even when weed-wacking or cutting your lawn to avoid new injury.
Example of a Drain - One recorded type of treatment
Image Citation (Photo 3): Tom Hall, Georgia Forestry Commission, Bugwood.org