Fuzzy Spots on Live Oaks in Katy, TX

WOOLY OAK GALL

Now that outdoor temperatures have come down, you may wish to visit your landscape again.  Don’t be alarmed if you see tiny tennis-ball shaped masses under the leaves of your Live Oaks Trees.  This is a Wooly Leaf Gall and is caused by a minute Wooly Leaf Gall Wasp.

A gall is an abnormal swelling of plant tissue in a reaction of the plant to specific stiumlus by the gall maker.  Galls are common on all types of trees.  In our case the plant produces this benign growth as a response from the laying of the wasp egg on the underside of the oak leaf and then the gall tissue surrounds the egg.  The wasp will go through total metamorphosis and use the nutrients of the host plant.  You may open the gall and see a green caterpillar-like specimen that is the larvae of the wasp.  There will be no long term damage to the host tree, except individuals that find this aesthetically appealing and breaks the twig for floral arrangements.
Prevention is not easy since it is impossible to determine which oaks will be selected by the egg-laying wasp and is not a wise use of insecticide.  Once the growth is seen it is too late to spray because the insect life cycle is protected within the encasement.  Systemic sprays  are not much help since the tissue to feed on is captured with the formation of the gall.  There are predatory wasps that kill these gall making wasp but are not in abundance in new communities where this problme is unsually seen.
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