Q: We planted two specimen Chinese elm trees early last spring after finishing our pool. One appears to have died. I noticed in the summer that bees appeared to be swarming around the base of the tree. Now they seem to have nested in the tree and are making something that smells very sweet. Do you have any idea what this is and how we can arrest the problem?
A: Your Chinese elm has slime flux. It is caused by a bacterial infection inside the trunk. There are actually two types of slime flux: “alcoholic” and “acidic”. The acidic flux smells like vinegar. The alcoholic flux smells like beer.
The condition is common on large oaks, poplars, elms and maples. It looks like the base of your tree was planted too deeply. If the lower trunk of a tree is underground, fungi and bacteria attack it and cause great damage.
An infection can also be caused by 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 external treatment for the condition. The tree will attempt to “wall off” the damage internally. 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 often periodic; it may disappear and not reoccur or you may see it every year.
Slime flux on Chinese elm
Slime flux damage higher on the trunk