University of Maryland Extension

Arborvitae Leafminer - Trees and Shrubs

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damaged tips of arborvitae

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.

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.

single arborvitae leafminer caterpillar
Arborvitae leafminer caterpillar


arborvitae leafminer frass
Tunnels and frass

arborvitae leafminer damage close-up
Closeup of damage

Management

To control light infestations, prune off infested tips. If the infestation is heavy, use a registered systemic insecticide in fall or early spring to control the caterpillars.

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