To distinguish rust mite damage from a nutrient deficiency, look at damaged needles with a hand lens. Tiny marks or scratches running parallel to the midrib of the needle can be seen on rust mite-damaged needles as if they had been rubbed with sandpaper. These marks won't be apparent if the rust-colored appearance is due to a nutrient problem. Damaged needles often drop off in the spring or prematurely in the fall. Pest description .
Rust mites are worm-like eriophyid mites similar to the rosette bud mite.
Rust mites have a wedge-shaped body with only four legs on one end. They can be found on both the upper and lower surface of the needle. They can be clear, tan, cream, or orange-colored and if viewed long enough with a hand lens, they can be seen to walk or rear up on their abdomens. With a dissecting microscope, clusters of tiny round eggs can sometimes be seen on the underside of the needles. Similar appearing problems .