Ask Mr. Smarty Plants

I consulted with Eric Beckers of the Texas Forest Service about the problem with your Taxodium distichum (Bald cypress).  He doubts that the neighbor's activities had little to do with it, unless they're spraying weeds along a fenceline with a herbicide.  One good possibility, however, is the current drought.  Eric says that the drought has been known to cause dieback in all sorts of tree species, including the usually tough-as-nails baldcypress.  This is especially true of those baldcypress that aren't growing very close to nearly permanent sources of water.  If the trees aren't near permanent water sources, natural drainage routes during exceptional droughts can be extraordinarily dry.  Additionally, the stress of the drought can make the tree susceptible to attack by pests.  It is pretty difficult to get close to the branches that are 30-40 feet up to see what might be causing the damage, but here are some possibilities that Eric suggested that you might be able to determine from the ground:

• If the whole branch is dying, it could possibly be squirrels.
• If the leaves are discolored over a large area and grading back to green, it could be spider mites.
• Clustered areas of thin and brown foliage, could indicate that there are bag worms

You can read about some of the "Damaging Agents" that do occur on the bald cypress from the US Forest Service.