Barklice on Oak: Harmless Web-Makers

The fine, silken webbing encasing your oak's trunk and limbs is produced by barklice (Archipsocus nomas), also called "tree cattle." They are not spiders, not pests, and not harmful.

What They Do

• Feed on lichens, algae, fungi, and dead bark tissue—essentially cleaning the trunk.
• Produce protective webbing that can cover the entire trunk and branches.
• Most visible July–August in humid conditions.
• Webbing disappears naturally by fall.

Identification

• Tiny (1/8 inch), soft-bodied, winged or wingless insects in groups under webbing.
• Move in herds—hence "tree cattle."
• No chewing damage, no honeydew, no plant injury.

Management

• None needed. They are beneficial clean-up crew.
• If webbing is cosmetically unacceptable: blast off with strong water jet.
• Do not spray insecticides—wastes money, kills beneficials.
• Fungicides reduce lichens (their food), which may reduce barklice—but fungicides aren't warranted for this.

Previous Insects

The black insects with long legs 3 years ago were likely a different species (possibly aphids or scale). Unrelated to current barklice.

Relax—your oak is fine. The webbing is temporary and harmless.