From:Austin, TX Region: Southwest Topic: Trees Title: Galls on live oak trees in Austin, TX Answered by: Nan Hampton
I am a resident of a condominium complex in Austin that has numerous Live Oak trees. Can you explain what the gall type things are hanging from the trees at this time of year and all over the grounds?
Are these trees diseased or is this simply a method of the trees spreading its seeds (other than acorns)?
The swellings you see on the live oaks are galls. They can be caused by various insects depositing their eggs in the plant. (They can also be caused by fungi, bacteria, nematodes and mites). The tree reacts by forming tissue around the eggs, and the insect's larvae develop inside the gall and feed on the gall tissue. The commonest cause of galls (the mealy oak gall) in live oaks in cities is a small wasp, Disholcaspis cinerosa. This tiny wasp has a two-stage life cycle and each stage produces a different type of gall. The wasps that emerge early in the spring from large spherical galls found on branches of the live oaks are all asexual females that lay eggs without mating with a male. Their eggs are deposited in leaf buds and their galls develop on the leaves. The adults that emerge from these leaf galls are both males and females. After mating, these females lay the eggs that form the galls that enclose the asexual females.
Some trees seem to be more susceptible than others to infestation. There are trees that seem never to have galls, and the ones that do get galls may have a heavy infestation one year and a light one the next year. Even those that are heavily infested seem to suffer little, if any, harm from the infestation.
Transplanting live oaks in summer July 17, 2008 - I have a need to transplant a live oak tree on a home building site. The need is now, the house is almost completely built out and the owners did not prep the site by moving trees or prepping them to ... view the full question and answer
Quercus polymorpha or Mexican white oak June 19, 2007 - On the Texas Oak Wilt Information Partnership website, they list a "Monterrey Oak" as one of the White Oaks (#3 in the FAQ section). I cannot find Monterrey Oak in your Explore Plants section; does... view the full question and answer
Arborvitae thinning in Bucks County, PA April 09, 2010 - My arborvitae trees are about 11 ft. tall. I had them put in about 3 years ago. They were 8 to 10 ft. when planted. After the first year, I have noticed they are thinning to the point where you can se... view the full question and answer
Bald cypress causing problems in Spring TX June 22, 2010 - There is a 50+ ft Bald Cypress growing near my property line. While the tree has grown substantial knees along the driveway and some as far as 35 ft from the tree in my flower beds, I do not see any d... view the full question and answer
Striped caterpillars on Cornus sericea (redtwig dogwood) September 07, 2011 - My red-twig dogwood has white/black striped caterpillars that congregate on the underside of the leaves and they are stripping the leaves. What can I do? They almost look like Monarch butterfly larvae... view the full question and answer