This appears to be a heavy population of Hemlock Woolly Adelgid, an unfortunately serious and widespread insect pest that can kill hemlock trees after a period of time. While hemlocks can be treated with insecticide to kill the adelgid (which perhaps the previous owner was doing), that would need to be repeated every one or few years for the life of the tree, and might impact other insects in the process (depending on the pesticide used and if its residues contaminate the windblown hemlock pollen). More information about this insect can be found on the linked page above.

Miri