Eriophyid mites, probably hemlock rust mite, have been detected in northeastern Illinois by Don Orton of the Illinois Department of Agriculture. Eriophyid mites are very tiny, cigar-shaped mites and are difficult or impossible to see without a hand lens or microscope. Hemlock rust mites feed on hemlock, causing the foliage to become bluish and then yellowish as feeding continues. Feeding is heaviest in the spring. This mite may also attack fir, yew, and spruce, particularly dwarf Alberta spruce, on which it may cause needle drop. Control with the miticides listed for spruce spider mite.