As with most tree troubles, there is no way to diagnose without first identifying the species, taking a first hand look at the site and obtaining a full history, however I am highly suspicious that your tree may be infested with the Douglas-fir Tussock Moth. The Douglas-fir Tussock Moth affects Douglas-fir, white fir, and blue spruce in Northern New Mexico, and can easily remove all foliage in a few years, usually starting at the top. The overwintered eggs hatch from mid May to early June and the baby caterpillars feed on the new growth. They are compelled to climb as high as they can to release a silk parachute to carry them away in a breeze in hopes of finding a new host tree, but most perish on the journey. This compulsion of the young to climb upward may be what causes just the top of the tree to die, but it is actually the mature Tussock Moth that does the most damage which can kill the rest of the tree.
Donna B. in Dixon, NM
Anthony of Baby Gorilla has helped us with pruning twice within the past five years, the first time on an ancient and beloved silver poplar and the second an apricot tree in front of our home. With the apricot tree, Anthony presented two choices for trimming, one a light pruning to enhance it as a beautiful spreading tree and the other a more intense pruning to help the tree bear larger fruit. Anthony and his crew did a great job pruning and with clean up. While he was at it, he removed a thirty foot high volunteer elm that was crowding out some of our small trees. We won the second pruning as part of Anthony's donation to the Dixon Volunteer Fire Department's annual pancake breakfast. Anthony is also a volunteer firefighter with DVFD.
Linda N. in Taos, NM
Anthony and his crew are very knowledgeable about trees and tree trimming! They were very courteous and professional which is why we have used them for several years.