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A. We have been alerted in our Master Gardener Training Course to be prepared to get calls during midsummer from homeowners who are alarmed about the appearance of mysterious webbing on the trunks of their oak trees! And, distressed homeowners generally want to know what pesticide can be used to get rid of the problem. Fortunately, the webbing is not caused by webworms nor tent caterpillars, but by a harmless insect commonly known as barklice.
It is important to understand that common name used for these insects is misleading as they are not lice. Except for their very small size (less than 1/8 inch long), they do not even look like lice. Barklice are brownish-colored insects that are gregarious. They live together underneath the protective layers of silken webbing.
The silk webbing produced by barklice typically appears in late summer (June through August). The webbing can completely envelop the trunk and large branches of a tree seemingly overnight. Its appearance may be associated with long periods of high humidity.
Barklice are small soft-bodied insects resembling aphids. Their web provides protection from predators while allowing the insects to feed. Although it gives the tree a “ghostly” appearance, the silk webbing–as well as the insects–are harmless and will disappear during the onset fall weather. Barklice live on the rough bark of hardwood trees, particularly live oaks and oftentimes on pecans.
You may wonder why barklice are being included as beneficial insects. As scavengers, they perform a valuable function in consuming excess accumulations of fungi, algae, dead bark, and other materials that occur on tree trunks and large limbs–in effect, they function as “Bark Maids” to help clean the bark of undesirable inhabitants.
Barklice do not eat leaves or the bark of the tree, nor do they damage the tree by boring into the bark. Although they may be viewed as unsightly, they are short-lived and harmless.
No control measures are recommended for these insects. Treatment is not recommended as the barklice are providing a beneficial service by helping Mother Nature to keep the bark clean and tidy!
Webbing produced by barklice typically envelop the trunks of trees (left photo) as well as large branches (photo above). Oaks and pecan trees are most commonly affected in the Upper Gulf Coast area.