En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
1 rating

Thursday - April 14, 2005

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Galls on live oak trees in Austin, TX
Answered by: Nan Hampton

QUESTION:

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)?

ANSWER:

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.

You can read a lot more about the mealy oak gall in "The Mealy Oak Gall on Ornamental Live Oak in Texas" and about other gall-makers in "Gall-Making Insects and Mites" from Texas Agricultural Extension Service, Texas A&M University System.
 

More Trees Questions

Will Prunus caroliniana (Carolina laurelcherry) be toxic to chickens?
July 25, 2010 - We are considering planting Carolina Cherry Laurels around our yard for dense hedging purposes. We are concerned because we have a small flock of free-ranging chickens who eat every seed and leaf in ...
view the full question and answer

Late leafing and early leaf-drop of Ohio buckeye tree
October 28, 2005 - We recently bought a house which has an ohio buckeye tree in the back yard. It stands about 40 feet from a large creek in Troy, Ohio. The tree is about 30 feet tall. A strip of the bark is missing....
view the full question and answer

Cherry laurels next to retaining wall in Austin
September 18, 2010 - My neigbors have 2 cherry laurel trees in their back yard planted within 4 feet of my retaining wall and fence. I am worried the root system will damage my retaining wall. The branches are already pus...
view the full question and answer

Trees to replace ones lost in Westchester County, NY
May 09, 2013 - We lost a large number of trees in the forest adjacent to our home, and I plan to replant them. What species do you recommend to plant the area with natives and to keep it looking "natural."
view the full question and answer

Replacement for non-native Italian Cypress in Austin
July 10, 2011 - I would appreciate your assistance with some native plant options to replace Italian Cypress trees in the Arboretum area of Austin, TX. I have 12 of the trees on the north side of the house to obstru...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center