Over the past several growing seasons, there have been more inquiries about the foul-smelling and unsightly seepage of sap from the trunk of shade trees that is commonly called slime flux or wet wood. It occurs in apple, birch, elm, hemlock, maple, mulberry, oak, poplar and willow. In North Carolina slime flux is very common in large, mature, landscape oaks, tulip poplar and elms. This disease is not normally a serious problem if the tree is otherwise healthy.
Slime flux is caused when bacteria infects the wood causing it to become discolored or appear water soaked (wet wood). Gas (carbon dioxide) is produced by fermentation by bacteria. The gas produces pressure in the wood. This pressure forces sap from the trunk through cracks in branch crotch unions, pruning wounds, lawn mower wounds, other injuries and occasionally unwounded bark. This oozing of sap is termed fluxing. The flux is colorless to tan at first but darkens up exposure to the air. As fluxing continues, large areas of the bark become soaked. Many different microorganisms grow in the flux producing a foul or alcoholic smell. Various types of insects are attracted to the slime flux.
There is no curative or preventive measures for slime flux except to maintain trees in a general good state of vigor and minimize wounds and injuries. More damage can be done to the tree in attempting to cure slime flux than the flux will do alone.