Question
I have a large oak tree (I think it's a live oak) probably 40+ years old. It has a web that covers the bark, not on the leaves. What is it and is it a problem.

Answer
This webbing is produced by small insects called bark lice and though the tree is apparently not harmed, the "ghostly" appearance may be somewhat disconcerting to the homeowner. The insects are probably common most years but are only noticed when populations are high and the amount of webbing becomes more apparent. When infestations are heavy the webbing may cover the tree including the main trunk, major and minor branches  and even the above ground portion of roots . However, although the webbing may cover virtually the entire bark surface, the foliage is not involved.

Bark lice apparently cause no damage to the trees and no control is recommended The webbing is quite thin and fragile and wears off as the season progresses. Heavy infestations seem to be associated with relatively long periods of high humidity,The good thing is that bark lice are nothing more than Mother Nature's cleaning crew, keeping the bark on our local oak populations clean and tidy.

Officially speaking, treating bark lice is not necessary because they cause no harm. Some homeowners think they are unsightly and wish them to be gone. If treatment is absolutely desired, there are some options available. One option is soapy water. A concentration of 2 tablespoons of liquid dish soap per gallon of water will affect bark lice. Removing the webs with a stream of water by itself will not kill the bark lice, but it will stimulate them to rebuild the webs within a few hours. Insecticide sprays to the trunk will control these insects as well.