Spruce Spider Mite Infestation on Emerald Green Arborvitae Hedge

25 Emerald Green arborvitae (planted 2001) show basal-to-mid-crown browning (5 ft up), upper 3–4 ft remain green. Classic spruce spider mite pattern.

Pest Profile

Oligonychus ununguis: cool-season mite, peaks spring/fall, declines in summer heat. Feeds on lower, interior foliage first—matching the symptom distribution exactly.

Monitoring

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

Control

• Insecticidal soaps (contact, thorough coverage)
• Acephate + fenbutin oxide (Ortho Systemic Insect Killer / Orthenex)
• Horticultural oil (dormant or growing season, watch for phytotoxicity)

Full canopy spray penetration is critical. Repeat per label. Avoid broad-spectrum insecticides that kill predators.