What can I do about the wasp infestation in my Live Oak?

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I have two oak trees in the front yard.  One is doing fine, the other is covered in ball shaped growths and I’ve been told they are wasp cocoons.  The poor tree looks spindly and weak.  The other tree looks great.  How do I treat this?

 

Thanks!

 

Kasey Laurent

Little Elm, TX

asked March 22, 2013

1 Answer

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The “ball shaped growths” on your Live Oak are called galls.  The most common Live Oak gall in North Central Texas is a brown sphere about the size of a quarter.  You are correct in that these woody growths are caused by a wasp.  However, this wasp is no larger than a fruit fly.  It “stings” plant tissue and injects a hormone that coaxes the tree to grow a chamber for one or more wasp eggs.  Within months, the egg hatches into a small grub that soon matures into a wasp.  Eventually the wasp leaves the gall structure through the exit hole that is apparent on most older galls.

This brown woody gall is commonly found on Live Oak trees in North Central Texas.

 While this gall is woody and persistent, anchoring to the specific stem for years, it presents no significant heath issue for the tree.   Why some trees can be heavily infested and others virtually untouched is a mystery to plant pathologists.  However, the wide diversity in oak species genetics is believed to play into the phenomenon.  Gall infestations do tend to run in cycles, just as other insect populations do.

 

 There may be other factors causing the two trees to not grow the same.  Water and fertilize both trees regularly and have a certified arborist inspect the tree if it fails to respond positively.