2014: Emerald ash borer is not known to be in Texas but, since its discovery in Michigan in 2002, has spread to Colorado and Kansas and will probably get here. The adults just eat foliage but the larvae kill trees. To date there have been tens of millions of ash trees killed in affected states. Texas has a very active emerald ash borer monitoring program underway and please let us know if you find any beetles that look like this.
Here are some links for additional information:
Dr. Mike Merchant's 2014 blog post with significant detail on this insect.
Report on discovery of emerald ash borer in Texas, and Texas A&M Forestry Service website for this pest. (Added 5/2016)