What's eating my oriental arborvitae?

Oriental Arborvitae (Platycladus orientalis) is most troubled by bagworms, which can defoliate entire branches. Spider mites cause bronze discolouration in hot, dry weather. Scale insects and juniper webworm also attack. Deer and rabbits will browse foliage heavily in winter when other food is scarce.

Silk and foliage bags hanging from branches; foliage stripped inside bags; branch dieback and plant death in severe cases. Hand-pick and destroy bags in autumn through early spring. Apply Bacillus thuringiensis (Bt) to young larvae in early summer. Spinosad or permethrin for larger larvae.

Fine bronzing or greyish stippling on foliage; fine webbing visible between branches in dry weather. Spray forcefully with water to dislodge mites. Apply miticide (bifenazate or insecticidal soap) during hot, dry spells. Avoid water stress.

White waxy scale crusts on stems and foliage; yellowing needles; premature needle drop. Dormant horticultural oil applied thoroughly in late winter. Systemic insecticide drench for established infestations.

Ragged browse damage to lower foliage and branch tips, especially October through March; young trees may be heavily disfigured. Install wire mesh guards or burlap wraps over winter. Apply deer repellent sprays monthly. Tall deer fencing for high-pressure areas.