Wetwood is caused by a bacterial infection and is very common in elms and many other species. The infection causes moisture to be retained in the wood and also produces metabolic gases that increase the internal pressures in the tree. Periodically the liquid will be forced out of the tree through wound sites. The liquid oozes out and down the tree, where other organisms colonize it. This liquid is called slime flux and is known to have a foul odour. 

Wetwood becomes a problem only when enough infection sites occur on the tree to compromise its structural integrity. A professional or consulting arborist should judge this. Otherwise, wetwood can be viewed as somewhat beneficial, as the moist environment that it creates in the tree helps to prevent decay fungi from colonizing the tree.  Symptoms appear as long discoloured streaks on the trunk.  Leaves may also exhibit some scorch if the infection is extensive.

At present, there is no treatment for wetwood.