Question
Hi, we have several tall tulip poplars on our property and recently we noticed that a tree on our front lawn has developed a wet line going down the front of the tree. My wife believes that this weeping issue could be a disease or bad sign. The weeping starts about 20 feet up and is very noticeable. If you believe this is a serious issue, how should it be treated. The tree is fairly large and maybe 15-20 years old although that is a guess.

Answer
Sounds like slime flux.
Slime flux or Wet Wood is a foul-smelling and unsightly seepage of sap from the trunk of shade trees. 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 a bacterial disease. The infected wood is frequently discolored or appears 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 upon 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. If the fluxing continues for months, leaves on affected branches may be stunted and chlorotic. Grass may be killed where the flux runs down the trunk onto the grass. Sap may continue to ooze for several weeks or months, but usually it eventually stops with no treatment and no apparent damage to the tree. This slime flux may be triggered by heat, drought and other stress.

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. If there is loose or dead bark  in the slime flux area, remove all of the loose bark and allow the area to dry. Do not apply a wound dressing.