Arborvitae Leafminers Arborvitae Leafminers Argyresthia sp . There are four species of arborvitae leafminers in the Northeast. Although the arborvitae leafminer Argyresthia thuiella is the most common in New York State.
Mined leaves have at first a translucent or straw color, later turning brown.
Mines start near the end of a branchlet in the scale-like leaves and extend into other branchlets. Injury begins in the summer and reaches a climax in the fall. Death of mined branchlets often occurs giving the tree a sickly appearance. The greatest injury probably occurs to hedge rows and ornamental plantings. The adults are active from late May to early June.