Slime Flux and Witches Broom by Jeff Rugg on Creators.com

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Slime Flux and Witches Broom

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 ten years old are more likely to get it than younger trees.

The bacteria enters the tree through exposed wounds such as from pruning cuts, damage from lawn mowers, 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 as the tree has more sap. It will stain the bark white and 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.

In the old days we would suggest to install 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.

Q: A couple of branches on one of our trees, sorry, I don't know what kind it is, have gone haywire. They have dozens of short branches coming out at every place the rest of the tree has just one or two branches.

Pruning the deformed branches off would make the tree lopsided, but this doesn't look good either. Any suggestions?

A: It sounds like the tree has a condition known as a witches' broom. The abnormal growth is caused when the plant no longer produces the proper amounts of growth hormones in the branch. The tip bud in a normal branch produces an auxin (hormone in a plant) that causes other branches down the length of the stem to not grow. The farther away the tip bud is the less influence there is from the auxin and the buds finally start growing.

In a witches' broom all of the buds grow all at once. In fact, many more branches than usual can start growing. Sometimes, only the end of the branch does this, so it really does look like a broom handle. Other times, all of the buds along the branch produce clusters of twigs, giving the branch a hairy appearance.

The condition can be caused by a virus, fungal infection, an infestation of eriophyid mites or insects, road salt spray and herbicide damage. Hackberry trees and sycamore trees are both commonly seen with witches' brooms. There are no treatments for any of the trees with witches' brooms. Since your tree only has a couple of affected branches, you could prune them out and suffer with the lopsidedness for a while.

Interestingly, some forms of dwarf evergreen trees are derived from witches' brooms. They are grafted onto new root stock plants and sold as dwarf plants or grafted onto a three-foot trunk and sold as a pompom.

Email questions to Jeff Rugg at info@greenerview.com. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.