Test Your Knowledge - September

A cluster of barklice
Eric Paysen, Clemson University


These are barklice, also called tree cattle because of their tendency to move along the tree in herds.

Barklice are small, soft-bodied insects that look similar to aphids. These insects belong to the order Psocoptera and are also known as psocids (pronounced so-sids). They are distant relatives of booklice, household pests that can consume wood and paper products.

Barklice cause no harm to the tree. They feed on fungi, lichens, and other organic debris found on the bark of the tree. As the barklice move around the tree they create a webbing to protect themselves from predators and from desiccation due to wind and sun. The barklice are small and usually go unnoticed until a heavy infestation occurs.

Webbing produced by barklice
Barklice webbing on a tree
Gerald J. Lenhard, Bugwood.org

Heavy infestations are related to long periods of high humidity. With a heavy infestation a thin webbing will become obvious on the trunk and branches. The small, ¼-inch long adult barklice can be found in herds under the webbing. The webbing does not interfere with photosynthesis and does not need to be removed since it primarily covers the trunk or branches, not the leaves.

Outbreaks of barklice are sporadic and most prevalent in the southern coastal plain of South Carolina. Since barklice are beneficial, it is best to just leave them alone. The webbing is thin and will wear off as the season progresses. While it is not necessary, a strong blast of water can be used to dislodge the webbing from a tree.

Millie Davenport
HGIC Extension Agent

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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.