Fine Webbing on Tree Trunks: Bark Lice (Psocids) Are Harmless

What Is That Silvery Webbing on My Oak and Crepe Myrtle?

If you see fine, silken webbing coating the trunk and large limbs of your oak or other hardwoods—especially in fall—it's likely bark lice (psocids), also called "tree cattle." They are harmless scavengers, not pests.

Identifying Bark Lice

• Webbing is on bark, not leaves or twigs.
• Under the webbing: tiny (1/4 inch), soft-bodied insects, brownish-black with roof-like wings (adults) or wingless (nymphs).
• They move in groups when disturbed—hence "tree cattle."
• Common along Gulf Coast to South Carolina; active in warm months.

What They Do

• Feed on lichens, fungi, dead bark, and organic debris.
• Do not damage living tree tissue.
• Webbing protects them from predators and desiccation.

Management

No control needed. They are beneficial clean-up crews. If webbing is objectionable, a strong jet of water will dislodge them. Insecticides are unnecessary and harm beneficial insects.

Fall Webworms: A Different Pest

Large, gray webs at branch tips enclosing leaves are fall webworms (Hyphantria cunea). They feed on leaves but rarely kill trees. Control options:

• Prune out small nests.
• Apply Bacillus thuringiensis (Bt) to foliage near nests.
• Use insecticides only if necessary; target young larvae.

Know the difference: bark lice on trunks = harmless; webworms on branch tips = cosmetic leaf feeders.