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Kali Zammit, Schmit, Rene G.  |  7/8/2015 9:31:30 PM

Fine silvery webbing encircling tree trunk produced by bark lice.

Adult bark lice psocids herding on tree branch.

This is the time of year when homeowners may notice the sudden appearance of fine silvery webbing surrounding the bark of a tree. Often the webbing will show up, quite mysteriously and overnight - surrounding upper areas of the trunk and/or a portion of one or more large main limbs. Generally when first noticed, homeowners become quite alarmed and concerned that damaging caterpillars, such as webworms or tent caterpillars, has infested the tree. The good news is that the webbing is the manufacture from harmless insects called Psocids or more commonly referred to as “bark lice”. Webbing formed by the bark lice serves as a camouflage against predatory insects and birds and aids in protecting the hundreds of tiny insects as they travel up and down the tree, feeding on and removing organic debris from the bark.

The common name “lice” is quite misleading for these special tree dwellers as bark lice are not parasitic nor or they even remotely louse-like in their physical make-up or appearance. In addition to their common identification as bark lice they are also referred to in other parts of the country by other names such as bark cattle or tree cattle. The reason for this reference is because they masse and congregate like a herd of cattle and when disturbed, scatter but reform back together again as a herd.

Bark lice are beneficial insects and pose no threat to the health and vigor of trees or to pets or to humans. Most often bark lice are found to habitat trees such as crape myrtles and various common oak species especially live oaks. They are scavengers that work in removing excess organic materials including algae and fungi from the bark of trees. Bark lice do not consume leaves, healthy tree bark or bore holes in a tree. Simply, they perform a beneficial function by helping keep the bark of trees clean and tidy by removing undesirable inhabitants!

Since bark lice are considered beneficial insects, no control measures are necessary or recommended. For homeowners not interested in the free clean-up service offered by the bark lice, the webbing can be easily removed with a strong wash from the garden hose. Often, the webbing on its own will disappear almost as quickly as it appeared - once the bark lice have cleaned up their act!

Rene Schmit is the LSU AgCenter County Agent for St. Charles Parish and assisting St. John Parish and can be reached at 985-785-4473 or 985-497-3261.
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