Test Your Knowledge - July

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A Test Your Knowledge Unknown
Slime flux streaks on trunk of hardwood tree.
Millie Davenport, ©2010, HGIC, Clemson University.

Yes, this is slime flux on the trunk of a tree. It is also called bacterial wetwood. Slime flux is caused by bacteria entering the tree through wounds on the trunk, roots, or branches. These wounds are usually the result of damage from lawnmowers or weed eaters, pruning cuts, or freeze damage. Slime flux tends to be a problem on hardwood trees such as maples, poplars, oaks and birches, although it can occur on other tree species. It may live in a tree for many years without any sign of infection. Once a tree is infected, fluxing may be triggered by heat, drought, or some other stress.

When triggered, bacteria will increase in activity. This activity will build up pressure inside the tree causing a clear sap to ooze. This process of oozing is called fluxing. At first, the sap may have a foamy appearance as it exits the tree. When the sap is exposed to the air, it darkens in color. As ooze runs down the trunk, it leaves water-soaked streaks that become gray or white when dry. The ooze may be slimy with a foul odor due to microorganisms growing in the flux. Grasses around an infected tree may die from this flux landing on it. In addition, various types of insects such as flies and wasps may be attracted to the ooze. Sap may ooze for several weeks or months, but luckily, slime flux does not usually kill a healthy, established tree. There is no cure or prevention for slime flux. Do NOT try to cure slime flux by using drain tubes or removing bark. These practices will just cause more harm to the tree.

Frothy slime flux oozing out of tree
Frothy appearance of slime flux oozing out of tree.
William Jacobi, Colorado State University, Bugwood.org

Homeowners have three primary issues with slime flux on a tree. First, the ooze leaves a water-soaked streak down the trunk of the tree. Second, the fluxing may produce a foul odor. And last, insects may be drawn to the ooze. If the insects or odor become a nuisance, apply a stream of water to flush the area. Commercially, slime flux will decrease the value of hardwood timber.

Timber with decreased value due to slime flux
Timber with decreased value due to slime flux.
Ron Jones, NC State University.

To minimize the effects of slime flux on trees, avoid wounding the tree, add a 3- to 4-inch layer of mulch over the root zone, and irrigate when there is a long dry period.

Millie Davenport
Home & Garden Information Center

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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.