There is a substance oozing from the trunk of my elm tree. What is this and what should I do to solve this problem?
— Jasmine Suarez, Skokie
Your tree appears to have slime flux, which is a very common bacterial disease that can occur in many kinds of trees, but is most common on elm in Illinois. It can also be found on trees such as oak, maple, redbud, sycamore, cottonwood and poplar.
Slime flux, also called wetwood, is normally not a serious disease. However, a tree with a chronic case of wetwood may decline in general vigor. The bacterium typically enters the tree through a wound, where it ferments and creates internal pressure.
Slime flux initially appears as a dark brown to black water-soaked area in the wood. Moisture containing the bacteria will then flow from cracks, wounds or other weak areas of the tree’s trunk. The liquid is colorless or pale, while the inside of the tree darkens when exposed to the air. When the liquid dries, it leaves a pale gray-to-white crust on the bark. A foul smell can occasionally develop due to secondary rotting organisms. Decay fungi do not prosper in the water-soaked wood on the trunk.
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There is no cure for slime flux, and in most healthy trees, this disease is not considered to be a life-threatening issue for them. The trees should naturally compartmentalize an injury or diseased area without any intervention on your part.
On occasion, a branch may die back if the liquid is transported through the tree’s vascular system. Prune the branch off if this happens and sterilize your pruning tools in between cuts to avoid spreading the disease. Provide supplemental water to your tree during dry periods and fertilize in the spring or fall to help reduce stress and improve the tree’s vigor. There is not much you need to do for your tree.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected]. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.