Arborvitae Rust Mites (Spider Mites): Treatment Worth It?

24-year-old arborvitae row under maple shade, heavily infested with "rust mites" (likely spruce spider mites). Neighbor's side brown; owner's side partially green. Question: will treatment restore appearance?

Pest ID

Spruce spider mites (cool-season mites). Tiny, pierce needles causing yellow speckling, browning, drop. Fine webbing in heavy infestations. Populations peak spring/fall; drop in summer heat.

Monitoring

Tap branch over white paper. Dozens per tap = treat. Recheck weekly.

Treatment Options (Homeowner)

• Insecticidal soaps
• Acephate + fenbutin oxide (Ortho Systemic Insect Killer, Ortho Orthenex)
• Thorough coverage of all foliage required.

Prognosis

If mites are controlled, arborvitae should regreen. Shade from maple complicates recovery but treatment is worthwhile.