Answer: Although the following resource is from Florida, there are photos of the symptoms of Lethal Yellowing which you might find helpful. http://edis.ifas.ufl.edu/PP146
If you suspect problems start by contacting BEXAR COUNTY Cooperative Extension, 3355 Cherry Ridge, Ste. 212, San Antonio, TX 78230 Phone: (210) 467-6575. Staff there can answer your questions and provide guidance.
Q&A Library Searching Tips