Question
I have three oak trees in my back which is fenced in into two sections and used for a dog pen. For the last couple months i have notices sap or some other kind of liquid at the base of the tree. This liquid also attracts the big yellow hornets, which by the way have stung my dog a couple times which cost a small fortune at the vet. My question is what can i do or purchase to get rid of the sap or bees so i can use this side of my pen. Please help.

Answer
The foul-smelling and unsightly seepage of sap from the trunk of shade trees is commonly called slime flux or wet wood. It occurs in apple, birch, elm, hemlock, maple, mulberry, oak, poplar and willow.

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. It has been a common practice with slime flux on American elms to drill a hole in the trunk and insert a pipe, which does not cure the problem. Inserting a pipe only allows the sap to drip on the ground and not run down the trunk and insert a pipe, which does not cure the problem. Inserting a pipe only allows the sap to drip on the ground and not run down the trunk.

Installing a drain pipe is not recommended in most cases because it does little good; moreover, slime flux on oaks occurs too close to the ground. 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.

I would spray the area with an insecticide for wasps. This will keep them from coming to the slime flux and also keep them away from your dogs.