Rust mites aren't a problem every year. They tend to be more of a problem during long springs with mild weather. They can be a problem on white pines and hemlocks as well as Fraser fir.
Online Information
CTN 34: Rust Mites in Christmas Trees - fact sheet with photos and information on the life cycle, scouting, and treatment threshold
Scouting for Hemlock Rust Mites
Focus on Scale Control - including miticide recommendations
HRM - Facts at a Glance - quick facts about hemlock rust mites on Christmas trees (1-page pdf version with photos)Photo Gallery
hemlock rust mite damage
mite-web
rust mites on white pine needles
