Harmless Barklice Create Webbing on Tree Trunks

Cottony webbing on oak or holly trunks, accompanied by tiny brown insects, is caused by barklice (also called psocids). They feed on lichens, fungi, and organic debris on the bark—not on the tree itself. The webbing protects them while they graze.

Barklice are harmless and beneficial; they clean the bark. The webbing washes off in rain or can be brushed away with a broom. No treatment is needed. They are common in humid, shaded areas and disappear when conditions dry.