Question
I have a healthy looking young red oak.  Suddenly, there is a lot of sap dripping down one of the branches and the trunk.  On close inspection, there is a small round hole in the branch that is covered with white foam.  There is no bad smell.  Is this white flux, or do I have an insect problem?  Nearby is a larger red oak that earlier in the spring also had a massive sap loss and is now in distress.  In addition, I live in very hot, drought-stricken north Texas.  Any information would be greatly appreciated.  Thank you.

Answer
Sure sounds like slime flux.
The oozing is called "slime flux" and is caused by a bacterial infection inside the trunk. There are actually two types of slime flux: 揳lcoholic?and 揳cidic? The acidic flux smells like vinegar.

The infection can be in a wound on the trunk surface or it can be deeper inside the trunk. In either case, bacteria ferment the tree's sap; it seeps out and down to the ground. Sweet-eating insects #wasps, bees, yellow jackets# would obviously be attracted to the damaged area.

There is no treatment for the condition. The best thing to do is to wash off the trunk to discourage bugs. Mix a pint of chlorine bleach in a gallon of water to make a final rinse. The flow of sap is periodic; it may disappear and not reoccur or you may see it every year.

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 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. 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.

Large mature landscape oaks have had problems with slime flux on the trunk or large exposed flare roots just above the soil line with no apparent wounds or injuries. 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. The best thing to do is to wash off the trunk to discourage bugs. Mix a pint of chlorine bleach in a gallon of water to make a final rinse. The flow of sap is periodic; it may disappear and not reoccur or you may see it every year.
Do not apply a wound dressing.  
I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of diameter scattered around the tree and watered in good. This will help improve the overall health of the tree. Since you are in a drought I would wait until this Fall to apply the fertilizer unless there come rain to again wet the soil.