Native Plants

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Wednesday - June 24, 2009

From: SAN ANTONIO, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Why are my Spanish Oaks dropping branches that appear to be alive?
Answered by: Jimmy Mills

QUESTION:

We have two large Spanish Oaks that we planted ourselves. They both have begun to loose large branches that aren't dead. These branches just break off and fall. There is usually a wind, but not to the extent that limbs should fall off the trees. Is this a problem with these trees? Can we do anything to prevent it?

ANSWER:

This doesn't sound like a problem of the Spanish Oaks so much as it sounds like the oaks have some unwanted guests; twig girdlers. These are a type of wood boring longhorn beetles that girdle twigs and branches and cause them to fall from the tree. Common hosts of the twig girdler include persimmon, pecan, elm, hickory, oak, honeylocust, hackberry, poplar, linden, redbud, basswood, dogwood and various fruit trees.

This Bulletin from the Texas Agricultural Extension Service describes the biology of the girdlers.

Have you examined the ends of the fallen branches? There should be some tell-tale signs if the beetles are the cause.

This article from the Alabama Agricultural Experinent Station has good illustrations of beetle damage.