Question
I live in Austin, Texas and have grouping of five Indian Hawthornes growing in a bed that runs along my back fence.  I also have some, evergreen junipers, annuals and Bradfored Pear trees in the corners of the same bed.  My back yard faces east, getting the morning sun.  I have one Indian Hawthorne that looks like it drying up.  Watering should not be an issue, as I had my back yard landscaped two years ago, when everything was planted and a complete irrigation system was installed, to water all the zones throughout my entire property.  My watering schedule is set according to my landscapers instruction. I'm wondering why this one plant is turning brown and drying up.  It is the the Indian Hawthorne to the far right of the grouping.  The plant to it's left is also beginnig to show signs of stress, (it's color is not as green as the others to it's left.  I'm wondering if disease is an issue?  All of my other landscape is vibrant and heathy.  Do you have any feedback or suggestions?

Answer
Mark,
First, I'd make sure that your plants are really getting the water that you think that they are - irrigation systems are famous for not reaching some areas well (but the drift makes the surface LOOK wet) and often these systems are set up to provide enough water for lawns but they aren't on long enough to deeply soak the area around tree roots.  Most plants do well with an inch of water a week - put a rain guage in the area where your Hawthornes are growing and see how much water the trees are really getting.

Next - Hawthornes are VERY prone to a disease called Fire Blight - it is bacterial, and makes limbs look dry, or as if they have been scorched by fire.  There are a couple of controls that registered pesticide applicators can use, but the first thing is to clip off dried and dead branches, dipping your pruners into a bleach water solution after each cut.  DO NOT FERTILIZE as this makes the hawthornes MORE prone to fireblight.  Make sure that the sprinkler doesn't spray the foliage of these plants frequently as this can also make the disease spread from plant to plant.

For an accurate diagnosis you might take samples and pictures into your local cooperative extension office, or to a certified arborist.

There are other rusts and fungi that attack hawthornes, but not that cause drying up.  
I  hope this helps,
C.L.