I'm sorry to hear about your tree!

From what I can see in the photo, that needle drop does look out of the ordinary, even for fall, when conifers will begin to lose their oldest needles.

Extensive needle drop around here is usually a sign of stress--possibly from disease or an insect attack.

The first thing we can try to rule out is a needle cast fungus. These are uncommon in Colorado because they don't tend to develop well in our dry air, but this year's extra rain has allowed a lot of fungal growth that we normally don't see. If you closely examine the needles that are dropping, you'd be able to see dark spots or streaks on them if you had a needle cast.

The second thing to try to rule out is Cytospora, a fungus that attacks branches and trunks. This one is more common here than needle casts. Look for sunken cankers on branches or the trunk of the spruce--focus on areas where the branches showing the worst symptoms attach to the trunk. or on their lower portions. The cankers can be bordered in a slightly raised area that can be covered in blue-grey resin, in which case they are pretty easy to see.

Third, you could have bark beetles like spruce ips. These tiny creatures develop under the bark of many conifers, destroying the vascular tissue and damaging the tree, often killing it. Look closely for pencil-lead sized holes in the tree that would indicate adult beetles leaving after development, or, if any areas are extensively damaged by the needle drop, you can peel back some of the bark on the trunk of the tree to look for larvae and meandering galleries that indicate their presence.

Finally, abiotic stressors can cause spruce trees to defoliate--these include drought stress, winter damage, or root damage from waterlogging, compaction, or construction. Can you rule these out as potential factors? Has any work been done around the tree this year?

Sorry not to have a "smoking gun" for you, but I hope this will help narrow down the cause.

Cordially,

John

Thanks for the reply. So the fact that the needles are shedding most from the branch tips and on the tree branches that are more shaded by the cherry tree doesn't provide any hint? I do not see evidence of disease.