San Antonio Express News
Sunday, August 1, 2004
By Nathan Riggs
Photos by Nathan Riggs
You would think that most shade trees would be content to display their beauty with expansive limbs and luscious, leafy growth. Lately, however, quite a few trees have tried another method of beautification: panty hose. Trees don’t wear panty hose!? Well, they don’t, on purpose anyhow. If they don’t wear panty hose, what is causing this silken sheen over the bark on the trunk and limbs? Webworms? Definitely not. Spiders? Nope. The answer: a little brown insect called the webbing bark louse.
Bark lice are small, brown insects that live on the rough bark of hardwood trees, especially live oak trees. Contrary to their name, bark lice are not parasitic on humans or animals, rather they live on the bark of trees feeding on fungi, lichens and dead insects. They serve as a “clean-up” crew of sorts for the tree. They do not eat leaves or bore into the tree, or consume the bark of the tree. Because they are small and vulnerable, bark lice can envelop the trunk of a large tree with a silken covering. This silk covering affords bark lice the protection from predators while they feed underneath.
Many callers are concerned that the silken covering on the trunk and limbs will smother the tree. Rest assured that this will not occur. Trees transpire, or breathe, through minute openings called stomata on the underside of their leaves. Since the webs are not covering the leaves, smothering does not occur. Since silk allows air to pass through, it is doubtful that smothering would even take place.
While it is perfectly normal to be concerned about trees wearing panty hose, in this particular case treatments are not recommended to control bark lice. Many local home improvement centers and similar stores whose staffs are not familiar with bark lice are recommending insecticide treatments for bark lice. Since they do no harm to the tree, why waste the money, time and pesticides on them?
Having said this, some homeowners feel it is absolutely necessary and more visually appealing for their trees to not wear panty hose. Virtually all insecticides approved for treating trees will control bark lice. Spraying the webbing off with water will only result in new webbing within a day or so.
All in all, the fact remains that bark lice are mysterious and unusual South Texas residents that appear from summer through fall. The webs disappear in late summer or fall and will resume their activities the following year.
This article was written by Nathan Riggs, Extension Agent-IPM with Texas Cooperative Extension in Bexar County. For more information please call 210/467-6575.