What's with all this webbing on my oak tree?

Lately, I have been noticing a lot of webbing on the live oak trees in the New Orleans area. I have also received a lot of telephone calls with concerns of why there is thick webbing covering the bark of old oak trees. This mysterious webbing is placed on the tree by bark lice (Archipsocus nomas), and aids in reducing the amount of predation on its population. Bark lice are often found under the webbing in clusters, and when the cluster is disturbed the cluster of bark lice scatter. These small insects were referred to as tree cattle in the older literature because of this herding behavior. The adult bark lice is brownish-black and approximately ¼ inch long, and the immature stage, or nymphs, are similar in appearance except they do not have wings. Bark lice feed on fungi, algae, dead animals and plants, and lichen found on the tree. Bark lice are considered not harmful to the tree, but rather somewhat beneficial. Although the webbing may be unsightly on your tree, the webbing appears from July and is more extensive in
as population numbers grow October. As a positive note, these insects decorate your trees with a natural Halloween decoration. If left undisturbed the bark lice will begin to eat their webbing as the population declines by the end of the year. Bark lice do not warrant any chemical control, and should not be sprayed.

Plant trees and shrubs in the fall and winter

The fall and winter seasons in Louisiana are the ideal times to establish ornamental trees and shrubs in the landscape. Many have the mistaken idea that ornamental plants should not be planted until early spring. This idea comes from catalogs and other online sources aimed at gardeners in the colder parts of the United States, where spring planting is recommended because soils are frozen and proper soil management cannot be carried out during the winter.

Fall and winter planting is the most ideal time to plant trees and shrubs in Louisiana because soil temperatures are high enough during much of this period to allow root development that helps plants get over the shock of transplanting before the hot weather ensues in the spring. Plant metabolism slows down in cooler temperatures and so do populations of insects; so, generally, plant maintenance is less intense in the fall and winter when compared to the summer. Planting in the fall gives the plant time to have an established root system that will yield great drought tolerance come summer when we don’t get much rainfall.  

In addition to the biological aspect of planting trees and shrubs in the fall in Southern Louisiana, nurseries will have their widest selection of shrubs and trees in the fall. For more information on maintenance and selection of urban trees, reference “Native Tree Growing Guide for Louisiana: the selection, planting and care of urban trees” at www. lsuagcenter.com