What's eating my degroot's spire arborvitae?

Degroot's Spire Arborvitae is a narrow columnar Thuja occidentalis. Deer and bagworms are its most damaging pests; the tall, slender form is still reachable by deer up to 6 ft. Spider mites cause summer bronzing. Arborvitae leafminer causes tip dieback that is often mistaken for drought stress.

Lower and mid-level foliage stripped; in hard winters deer will stand on hind legs to reach higher growth Deer repellent spray; burlap wrap in winter where deer pressure is heavy; fencing where multiple plants are grown as a hedge

Bags can go unnoticed in the dense columnar interior until defoliation is severe Inspect the interior of the crown in early summer; Bt or spinosad spray in late June

Inner foliage turns bronze then brown; most apparent on the south-facing, sun-baked side Horticultural oil spray; improve air circulation by spacing plants adequately

Tips of branchlets brown and die; hollowed shoot tips with tiny pinhole exits Prune affected tips; systemic insecticide applied in mid-May to intercept flying adults