people notice fine silken webbing on the trunks and branches of their
trees during the warm summer months. The assumption is that this is a
problem but the insects that cause this webbing are not harmful to trees.
They could even be considered beneficial.
The tiny insects that make the webbing are called psocids
(pronounced so-cids). They have numerous common names including tree
cattle and bark lice. Basically, they feed on lichen, moss, algae, fungi,
spores, pollen and possibly the remains of other insects found on the
tree’s bark. As a result are sometimes referred to as bark cleaners.
the webbing appears suddenly on a tree’s trunk and/or limbs, many
homeowners wonder how it got there, where it came from and if it will
damage their tree. The cause for the webbing can be seen if the webbing is
pulled from the tree. Underneath you’ll see brownish-black insects
approximately ¼ inch in length with some white markings. When the webbing
is removed, the insects usually move away in a group and are commonly
called tree cattle because of this herding habit.
cattle do not damage trees. Some people will see the webbing as it
glistens in the sun, walk to the tree and visually inspect it from top to
bottom - much closer than they’ve ever inspected the tree. It was the
webbing that got their attention. They might notice a dead branch or other
imperfections in the tree and then wrongly blame 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. I talked to one person that cut down a tree after finding the
webbing assuming he was dealing with a pest that was going to move through
his neighborhood and kill other trees.
female psocids lay their eggs in clusters on leaves, branches and tree
trunks. After hatching, the immature insects (nymphs) remain together
under their silk like webbing. The web serves as a protection from weather
and predators. In the adult stage, the wings of this insect are held
roof-like over their body. The nymphs are wingless. Psocids usually have
several generations per year in
seeing the webbing, many people insist on spraying psocids with
insecticides because of the concern that these insects are damaging their
trees. But as mentioned, they are bark cleaners and do not damage trees.
If the webbing is considered unsightly, a heavy stream of water from a
garden hose can be used to wash insects and webbing off infested trees.
nothing is done, the webbing usually goes away in several weeks. Psocids
can be found on many rough-barked hardwood trees and palms. Most people
seem to find them on oaks more often than other tree species, though.
additional information on
insects, contact your
Florida Extension Office
or visit the
’s Website, Featured
Creatures, at http://creatures.ifas.ufl.edu.
Williams, Extension Horticulture Agent,
, Revised August 14,
2006. For additional
information you may call 689-5850 or 729-1400 extension 5850.