TREE CATTLE ARE HARMLESS, by Larry Williams UF/IFAS Extension Agent







people are noticing small insects on trunks and branches of their trees. When
disturbed, these insects move in a group and are commonly called tree cattle
because of this herding habit. They are 1/4 inch brownish-black insects with
white markings.

Some people assume that
these insects will injury their trees but they are harmless. They could be
considered beneficial.

These insects are called
psocids (pronounced so-cids). They have numerous common names including tree
cattle and bark lice. They feed on lichen, moss, algae, fungi, spores, pollen
and the remains of other insects found on the tree’s bark. As a result, they
are sometimes referred to as bark cleaners.

Tree cattle may form
webbing. This webbing is tight against the tree’s trunk and/or limbs. It
appears suddenly. The webbing is used as a protection from weather and
predators. Underneath you may find psocids.

glistening webbing may attract a person’s attention resulting in the tree being
visually inspected from top to bottom. A dead branch or other imperfections in
the tree may be noticed and then wrongly blamed on the tree cattle. I’ve talked
to homeowners that sprayed their trees with insecticides or that hired pest
control businesses to treat the trees as a result of finding the webbing/psocids.
One person told me that he cut down a tree after finding tree cattle. He
wrongly assumed that these insects were pests that might move through the area
and kill trees. He thought he was doing a good thing.

Adult female psocids lay
eggs in clusters on leaves, branches and tree trunks. After hatching, the
immature insects (nymphs) remain together under their silk webbing. Adults have
wings which are held roof-like over their body. Nymphs are wingless. Psocids
usually have several generations per year in Florida.

seeing the webbing and/or insects, many people insist on spraying insecticides
because they believe these insects are damaging their trees. But as mentioned,
they are bark cleaners and do not damage trees. If the silk webbing is
considered unsightly, a heavy stream of water from a garden hose can be used to
wash insects and webbing off infested trees. If nothing is done, the webbing
usually goes away in several weeks.

Psocids can be found on
many rough-barked hardwood trees and palms. Occasionally, they may be found on
wood siding, fence posts or similar areas.

additional information on Florida insects, contact your University of Florida
Extension Office or visit Featured Creatures at

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