Tree Problems

Jeff Rugg discusses some specific tree diseases and what you should and shouldn't do to manage the disease. (tawanroong/Shutterstock)

Q: The elm tree in our front yard has a disgusting, brown, slimy mess running down the trunk. As it dries, it is leaving a white streak on the bark. What can we do to stop this?

A: Your tree has a bacterial infection called slime flux or wet wood. Many tree species can get this infection, but for some reason, practically every elm tree is affected to some degree. Trees over 10 years old are more likely to get it than younger trees.

The bacteria enter the tree through exposed wounds, such as pruning cuts, damage from lawnmowers, cut roots, storm damage, and where two trunks grow together. As the bacteria consume carbohydrates and cellulose, they release gases. The gases create pressure that pushes sap out of the tree trunk. The sap may include some of the bacteria, but on the surface of the trunk, it can become contaminated with yeast and other organisms.

It often becomes a stinky and unsightly mess running down the trunk. It seems to run more during wet weather. It will stain the bark white, and it will not wash off easily. The slime is toxic to the surrounding live tissue in the trunk, but it won’t spread and kill the tree by itself.

We used to suggest installing a drainpipe into the tree to relieve the gas pressure, but it doesn’t do any good, and installing the pipe damages the tree. If the tree is otherwise healthy, it will probably stay that way. Just rinse off the slime while it is still wet to get a little less of the white stain on the trunk.

Q: We have a sycamore tree that has had a problem leafing out in the spring during the past two years. What can we do to help keep it healthy?

A: Sycamores often get a serious fungal disease called anthracnose. Other tree and shrub species get anthracnose problems, but the symptoms are worse in sycamore trees.

It attacks and kills the leaves and small twigs. It attacks the trees in the spring when the weather is cool and wet. All the new leaves are killed until the weather warms up and dries out and the fungus cannot spread. The fungus remains dormant in the litter that falls off the tree.

Over the summer, new branches of leaves will grow. They may die next spring. All of the short, dead branches on the ends of long branches give the tree the visual effect of looking like a tree made from a bunch of broom handles.

During the summer, remove any dead leaves and twigs from the ground around the tree. A sick sycamore tree uses a lot of stored food to produce leaves and branches that are killed in the spring. It then has a shorter summer season of healthy leaves to produce the starches that it needs to survive the winter and grow new leaves next spring. To keep the tree healthy, water and fertilize it during the summer. Sycamores are native to lowlands, so they need more water than a typical suburban landscape tree.

Next spring, when the new growth begins to sprout, the tree needs to be sprayed with a fungicide weekly until the weather warms up.

Sycamores are pretty trees, but they do not make good urban landscape trees for small landscapes. They have an unusual white bark that is produced by dropping the corky outer layers of bark onto the lawn, adding to the maintenance.