arborvitae leafminer symptoms

Arborvitae leafminer damage. Photo: Connecticut Agricultural Experiment Station , Connecticut Agricultural Experiment Station, Bugwood.org

Updated: April 21, 2021

Key points

  • 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.

Management

  • 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.

Rev. 2020