Out of the 100 I planted, 5 have survived including the one I just found. IMHO, tubes would have help.

First off, if you are seeing small trees 'disappear', it's most likely mice or rabbits chewing them off.

Leaf eating insects usually will leave the woody part of the stem as evidence.

The thing I like the most about tree tubes for deciduous seedling and saplings is, it protects them from voles (mice) and rabbits for the next several years, if the tube is tight to the ground. And protects from deer for the next year, possibly more.

Once the top of the tree emerges from the top of the tube, deer can happily prune the tree off as fast as it can grow. Once that issue is imminent, some sort of taller protective mesh surround and stakes is necessary.

You need pretty strong stakes to prevent deer from upsetting tree protection of any kind.

I just drove by a field where at least a hundred small trees are protected by tree tubes, the ones sold by our district soil & water conservation office. They have a pretty good stake on most of them but you can see several down the line that have been knocked over by wind and perhaps deer, exposing the tree.

Another thing about tree tubes is, generally, a smaller seedling will grow up as a single leader, until it exits the top of the tube, resulting in reaching the height of a tree tube faster than if open grown. I've seen this both on an Acer rubrum and Gleditsia triacanthos, that I've grown here from small seedlings.

I don't think tree tubes will completely protect a small tree from all kinds of insect damage, though tubes appears to alter the environment inside the tube enough that it may deter some of the insect nasties from making themselves at home. I can only say I've never experienced insect damage on any of my trees with tubes on them. :-)