- Arborvitae leafminer is a pest of arborvitae in the northeast. Other similar leaf-mining caterpillars attack junipers.
- Caterpillars cause damage by tunneling in the tips of foliage causing them to turn yellow then brown. The yellowing appears in late summer and worsens the following spring.
- Damage is usually most severe on the south side of plants.
- Mature caterpillars are 1/4 inch long, green with a reddish tinge, and black heads. The adults are 1/3 inch long, light tan moths.
Checking for the pest
- To monitor for this pest, look for brown tips among the green foliage in spring and fall.
- The damage is usually first noticed on foliage in full sun.
- Break open the yellow or brown tips and look for tunnels, frass, and caterpillars.
- The caterpillars are present from late summer through the following spring.
- Shake the foliage in June and July to detect the small, light tan moths.
- To control light infestations, prune off the infested tips. If the infestation is heavy, use a registered systemic insecticide in fall or early spring to control the caterpillars.