Bark lice are harmless to trees

By Lisa Stewart
Extension County Director
Webster County

Because YOU asked

“I keep seeing groups of these insects (pictured) on the trunk of our crape myrtle trees. Are these things damaging my tree?”

According to Dr. Blake Layton, no, bark lice are harmless insects that feed on fungi, lichen, pollen and other organic materials they find on the bark of trees and similar sites.

Many species of bark lice are in the state, but this particular species, which is sometimes called the veined bark louse, is the largest and most conspicuous, and it occurs throughout the state.

The wingless nymphs and winged adults form quarter-sized to palm-sized clusters and move about in “herds” over the tree trunk as they “graze.” Because of this behavior, bark lice are also referred to as “tree cattle.”

Although this species occurs on many different species of trees, it is most often noticed on crape myrtles, probably because they are so conspicuous on that smooth, light-colored bark.
Along the Gulf Coast, gardeners sometimes encounter a different species of bark louse, the webbing bark louse. Webbing bark lice spin a fine layer of silk that protects them from predators and other hazards. During years of high populations, trunks of large oak trees may be entirely encased in this fine, white silk, which, except for the strange appearance, is also harmless to the tree. Veined bark lice do not produce silk in this way.

This column is made up of questions presented to the Webster County Extension Service. Please get in touch in person or by phone (258.3971) or e-mail (lisa.stewart@msstate.edu) if you have questions you would like to see discussed here.