En Español

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

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

Identification of pines on I35 between Dallas and Denton
May 03, 2011 - I frequently drive I-35E from Dallas up to Denton and I've often wondered if the pine trees that I see near the road and in the surrounding areas, especially between Lewisville and Denton, have been ...
view the full question and answer

Allelopathy in Sassafras albidum
January 11, 2012 - Sassafras albidum description says "Sassafras is allelopathic and can discourage the growth of certain other plants within its root zone." My question is: WHICH plants are susce...
view the full question and answer

Growths on Shumard Red Oak leaves from Katy TX
April 01, 2013 - Our beautiful Shumard Red Oak has developed lots of light green grape like growths on the leaves. Please inform us what this could be and how we should treat it?
view the full question and answer

Best fertilizer for live oak trees in Central Texas
April 22, 2010 - What is the best fertilizer for live oak trees in Central Texas?
view the full question and answer

No acorns on mature live oak in Little Rock AR
April 18, 2010 - Why does my very large mature live oak have no acorns?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center