Question
The top of one of our blue aptos redwood trees looks like it is dead.  The tree is about 40 ft tall and  it's the top 4-6 ft that is all brown and looks like a dead tree.  It's located in the middle of your other 12 redwood trees. The neighbors did have a blight in their trees years ago. Those trees were removed but I don't know how long that germ (?) sticks around.  
Is there a way to tell what is happening to the tree and/or what we should do for it.  

Thanks for any help you can offer.        Babs

Answer
Hi Babs:

The affected area probably has some type of decay within.  This can be cause by any one of numerous fungal or bacterial microorganisms.  The decay is usually a slow, yet progressive process.  If the tree is cared for by watering etc, it may persist for many years- but ultimately somewhere down the line it will need to become firewood, especially before it begins to pose a hazard to persons or property. Many of these organisms can survive on dead wood/tissue indefinitely.  You may consider having the overall health status evaluated by a licensed arborist or plant health official.

Regards
Steve