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Why is my tree’s trunk oozing black stuff?

Why is my tree’s trunk oozing black stuff? This is a question we get asked often. Well, the answer is slime flux. Another name is bacterial wetwood.


Bacterial wet wood is a bacterial infection that attacks the trees trunk. As the bacteria multiply, it creates pressure within the trunk that escapes through the trunks bark and typically looks like a black oozing slime from under the bark.

Many times with bacterial wet wood during the warmer months, because of the sugars in the tree mix with the bacteria, it causes the sap to ferment creating alcohol.  Two years ago, one tree I saw had a particular bad case of slime flux. I observed multiple wasps and bees stumbling around and falling off of the tree drunk from the alcohol.   Her case was remarkable because I could smell the alcohol from 10 feet away. There was a lot of oozing out of this tree.

Bacterial Wetwood/Slime Flux Treatment- (Surface only)

Treating bacterial  wetwood is temporary at best. They used to recommend drilling holes within the tree in an attempt to relieve the pressure out of the interior portions of the tree. However this remains debatable as any sort of drill bit can potentially introduce bacteria deeper into the tree.

Either way, one accepted method  of treatment,  albeit surface treatment only,  is to simply mix one part  bleach to nine parts water and apply liberally to the trunk every couple weeks. Essentially this will kill off any bacteria on the surface and help  protect the trees bark layer staving off early delamination and introduction of decay. However, be aware that if your tree has bacterial  wetwood, likely  it will heavily affect the tree causing a decay pocket and perhaps weakening the structure overall. So you might want to mentally prepare that the tree  may eventually have to come down because of this infection.

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