Pensacola News Journal

For:  Saturday, July 6, 2002

By:   Daniel E. Mullins
        Extension Horticulture Agent        Santa Rosa County

 

Fine Silken Webbing on Trees No Cause for Alarm

 

A fine, silk-like webbing is being seen on the trunks and branches of many trees in the area.  This is the work of small insects known as Psocids, commonly called bark lice or tree cattle.

Signs of their presence range from small silk covered patches on a tree trunk to the entire trunk and branches being covered.  A few years ago, when the movie “Ghost Busters” was popular, a child told me that their trees had been “slimed.”  In cases where Psocids are present in high numbers, trees can truly take on an eerie appearance.

Psocids are actually bark cleaners and do no damage to the trees where they occur.  They feed on fungi, spores, lichens and other debris that they find on the tree’s bark.  The fine webbing that they produce is evidently to protect them from predators or to create a more favorable environment underneath.

These are interesting insects due to their appearance and habits.  Adults are approximately 6 millimeters long.  The body is brownish-black with white edges and stripes on the wings, which are held roof-like over the body.  The nymphs, or immature stage is wingless.

They were given the common name “tree cattle,” not because of their size but because of their peculiar “herding” habit.  These insects are gregarious, feeding in clusters several inches in diameter.  When approached, the entire group moves in the same direction at the same time.

Psocids are not found on all local tree species.  They are attracted to those with rough bark.  Obviously, the more cracks and crevices that a tree trunk has, the more bits of organic material lodges there, providing food for them.

Unfortunately, I have heard horror stories related to Psocids.  There are cases where homeowners have had trees unnecessarily removed upon seeing layers of silky webbing on the branches.

These web covered branches might appear to be serious but this is a condition that can be ignored or even appreciated.  Allow these little insects to go about their business of cleaning the bark.

They usually complete their life cycle after a few weeks and the webbing gradually disappears.  Homeowners who find the webbing objectionable can use a garden hose to wash it off.

 

Question of the Week:  My hibiscus plants are taking a long time to begin flowering this year.  Could this be because of cold injury?

Answer:  Yes.   Most hibiscus, with the exception of 3 or 4 native species, are tropical or subtropical plants.  Any that were growing in the ground, or were left outside in pots last winter sustained varying degrees of cold damage.

Any above ground growth that was killed due to freezing temperatures resulted in the loss of a significant amount of stored energy.  Consequently, the plant will take longer to flower because it must have time to grow and build up enough energy to begin flowering again.  Be patient.