En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Galls on live oak trees in Austin, TX

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

Propagation of Mexican olive in Luling, TX
August 04, 2009 - Mr. Smarty Plants: we live in Luling, just south of Austin and have a 4 year old Mexican Olive tree; question: how do we propagate this 'hard to find' tree? Thank you so much.
view the full question and answer

Native tree for Perrysburg OH
March 25, 2009 - Can you recommend a small tree 15-20 feet for Perrysburg Ohio that does not produce seeds/berries/nuts etc, has large leaves and is pest resistant? Low maintenance
view the full question and answer

Mexican Plum with wilted leaves in Austin, TX.
June 06, 2012 - I am new to Texas & have a yard with mature mexican plum trees. They are quite beautiful however as summer sets in I notice that the leaves appear "wilted". Is this normal or should I be providing...
view the full question and answer

What is eating the leaves of my oak tree in Cedar Park, TX?
May 25, 2010 - This one has a couple of arborists stumped. I have clusters of small, light-colored worms on the leaves of an oak tree, but no tents or webs. They are eating the chlorophyll in the leaves, leaving th...
view the full question and answer

Care for indoor Lemon Cypress
November 30, 2008 - How do I care for an indoor Lemon Cypress tree?
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