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 the 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.
The species of barklice most commonly encountered in the Galveston-Houston region is the brownish-colored and gregarious Archipsocus nomas. They live together underneath the protective layers of silken webbing. The silk webbing produced by barklice typically appear in late summer (July and 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.
Another closely related species of barklice may also be encountered the Galveston-Houston region: Cerastipsocus venosus. Members of this species are noticeably larger and less commonly encountered than their web-forming cousins. Adults are about 1/4 inch long and have shiny black wings, which are held in tent-like fashion over their abdomens. Members of Cerastipsocus venosus are also gregarious and typically encountered as a colony.
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!
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
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