Host an Event Volunteer Join Tickets

Support the plant database you love!

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
2 ratings

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

Problem with baldcypress tree
May 27, 2011 - Two of my three 20 year old Bald Cypress trees appear to have leafed out but are now brown in parts of the tree. The brown area is at the tops of the trees which are probably 40 ft. high. They were...
view the full question and answer

Oaks at Wildflower Center from Wimberley TX
September 05, 2012 - I know you have numerous Quercus fusiformis examples at the ladybird Johnson Wildflower Center. My question is, do you also have Quercus virginiana growing there? Also, is Oak Wilt a disease that ...
view the full question and answer

Need help with a misshapen Monterey Oak in Austin, TX
March 11, 2010 - In the Fall of 2008, I purchased a very tall Monterey Oak from TreeFolks at the Burger Center Sale. Since the wind was so high, all the tall trees were on the ground, and I guess that is why I did no...
view the full question and answer

Fast growing shade tree for East Texas Piney Woods
April 11, 2013 - What is the fastest growing shade tree for E.Tx.Piney Woods? We have an area that desperately needs protection from the summer heat. The site is comprised of gumbo clay and there are no other plants t...
view the full question and answer

Possibility of symbiotic relationship between cedar elm and ashe juniper
November 14, 2006 - Is there a symbiotic relationship between cedar elm and ashe juniper? We have a small ashe juniper sapling and a small cedar elm sapling growing near each other (actually, we planted the juniper 2 yea...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.