Western Hemlock dying form top down

I have two of these trees on my property, The one in the backyard was looking unhealthy the year after we moved in, but it didn't bother me as I was planning to remove it anyway for a woodshed. One of those things we haven't got to. The second tree is in my front yard and it shades my living room window. I truly do love this tree and now it is dying from the top down at a rapid rate! I'm resigned to the fact that now they both have to come out, but I have no idea what is killing them. There aren't many hemlocks in this neighborhood (surpisingly!) mostly cedars and black cottonwoods. I have never noticed pests on the tree itself, there is no oozing sap or bark damage. Only the needles are turning brown and falling off from the top down. I usually remove the lowest two branches every other year as the tree grows (so I've done this twice this spring being the second time), but that is all that I have done to it.

Any ideas??

No way to save - I have lost several in the past couple years.
The culprit is the Hemlock Looper. They feed voraciously and defoliate the upper crown; by the time you notice the dieback it's too late.
Apparently, you can have Bacillus Thuringiensis vr. kustaki (a microbial insecticide, specific to the looper larvae) sprayed on your Hemlocks during the first year, and this will help protect the tree. The question is - would you notice the damage at that time? My Hemlocks were tall, so it would have been difficult.

I guess the silver lining here is a get to pick out a new tree!! After all the hard work of removing this one.

I had no idea there was something wrong. The tree has always looked great and looked it's same, happy, thriving self this spring. Then one day I looked up and noticed the top was dead. I had no idea I could have done something to protect it.

Thanks for your help.

It was a surprise to me, too. I really like the form & colour of the Hemlocks. So to lose them was huge. I wish the doug firs I have were afflicted instead, but no - they are happy & healthy.

See, that's the way I've been feeling about the cedars. They're just not a favorite of mine!! To loose the hemlock is very disappointing. I love their long straight trunks and they have an elegant canopy.

Now it's an eyesore. It's like having an obvious stain on your clothes and being miles away from a change of clothes. I want to put a sign out in the yard, "Sorry, I know the tree looks awful. I'm working on it!"

Western red Cedars? I do not like them either. They are not true cedars, just as Doug firs are not true firs.
The first one that died was in the midst of others - not too bad because I could only see the top. During the windstorm last December, the top 30' snapped in the wind & landed in my veg garden, as if perfectly placed: it was parallel to the fence & did no damage. We just had them taken down a few months ago, and it isn't cheap to do. But the hardest thing is to get used to them not being there. I have way too many tall evergreens on my property, and wish i had logged it 20+ years ago, replacing with large deciduous trees, along with some of the better evergreens, like some of the pines, true firs,true cedars and 1 Ginkgo.
Oh well, that's life...

Well wasn't that a nice bit of providence!! Our neighbors tree took out our powerline in the windstorm and we camped out for a week. I was a great reminder of all the things we need to do to prepare for an emergency and I think we're better prepared now!

Our neighbor is a logger, so hopefully he'll be willing to help us and share the wood.