A Technical Report from The Bartlett Tree Research Laboratories
Arborvitae leafminer (Argyresthia thuiella Packard) is one of four eastern species of leafminers whose preferred hosts are plants in the genus Thuja. While the insect is commonly found throughout the Northeastern United States and adjacent portions of Canada, its range includes parts of the mid-Atlantic and Midwest. Arborvitae leafminer is a moth (order Lepidoptera) in the family Argyesthiidae, a group described as “shiny head-standing moths” because the adults will often rest with their head against a surface and their body angled upward. As the name suggests, caterpillars of this species create mines within arborvitae branchlets which can result in local plant tissue discoloration and crown dieback.