A month ago, I was at a physical therapy session with Lisa at her studio (http://www.movemoretoday.com/) and she pointed out to me a Bagworm problem she was having on several of her plants outside. I had never noticed them before and went home to survey my trees to see if any had indeed found their way here as well.
I did have some!
I had passed a spruce tree several times, not really noticing them as
they are well disguised as pine cones.
Our tree had between 50 and 100 bags. John used a ladder to reach and remove them by hand,
then discarded them in the trash.
We still have a few that still need to come down.
If not removed, when they hatch in late May into June, 500 to 1000 worms will emerge from EACH bag and eat all the needles, the bark and can completely defoliate the tree or bush.
Had I had them before and never noticed them? It's possible as they have a natural predator and infestations can vary from year to year. They also spread very slowly.
If you have them though, be proactive and remove them immediately.
See the following Penn State website for further information: http://ento.psu.edu/extension/factsheets/bagworm