[svcw]

When I lived in the mountains I was told by the tree cutter that the beetles only attack unhealthy trees.
I would think it is all part of natural selection in the forest.
But hey I could be wrong.

[CowboyJay]

I would think it is all part of natural selection in the forest.

No. They all get hit. The 90% tree mortality rate in infested areas is not a misprint. We have literally entire mountainsides full of dead trees in Colorado right now. One good hard winter would clear it up, but we haven't had one in a good decade.

[george76]

They may be faster on unhealthy trees, but kill healthy ones too.

Never seen that they eat on dead wood.

picture from colorcountry

[moondoggie]

When I lived in the mountains I was told by the tree cutter that the beetles only attack unhealthy trees.

That "used" to be true before Colorado underwent a 10-year drought when all the trees got stressed from lack of water making all of them ripe for the pickings.

[editor-surveyor]

"I was told by the tree cutter that the beetles only attack unhealthy trees."

Not so. Their attack is certainly more devastating on a tree that has a poor water supply, but without the beetle, the tree would live on for decades.