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How to identify it
- The giveaway is brown tips that are hollow inside and hold frass and sometimes a living larva; brown tips that aren't hollow point to winter injury, disease or another cause.[1]
- Larvae are green, sometimes reddish-tinged, or brownish caterpillars up to about 1/4 inch long with a dark head.[2]
- Adults are tiny silvery tan to light gray moths with brown and black spots, about 1/8 inch long.[1][2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Winter injury | Leafminer browning often doesn't show until late January or February, so it is easily mistaken for winter burn; check whether the brown tips are hollow.[1] |
Where it lives
A pest of arborvitae in the eastern United States; UMass notes that related Argyresthia leafminers, including one on eastern redcedar, cause similar damage.[1][2]
Biology and life cycle
Adults fly from late spring into early summer and lay eggs on the foliage; newly hatched larvae bore into the scale leaves and mine from the tips toward the base.[1][2]
Larvae feed until fall, overwinter in their mines, resume feeding in spring and pupate inside the mine.[1][2]
Damage and signs
- All arborvitae varieties are attacked, with American pyramidal, globe and golden arborvitae preferred; NC State notes it may also attack juniper.[2]
- Mined tips turn yellowish or whitish, then brown, and whole shrubs can brown; heavy attacks can make leaves drop or, rarely, kill a plant, though arborvitae usually survives with reduced looks.[1][2]
Health risk
Control
Prevention
To check for adults, gently shake the foliage in June and July and watch for moths; yellow sticky cards don't work for this pest.[1][2]
Traps and physical control
Prune out and destroy dead tips later in the season so moths can't emerge from them the next spring.[2]
Biological control
At least 26 kinds of parasitic wasps attack it, and after two or three years of rising numbers they can sharply reduce the population.[1][2]
Pesticides
If numbers stay high, sprays aimed at adults during the flight period or systemic treatments once larvae are inside are the options; follow the label.[1][2]
Common questions
- Why are the tips of my arborvitae brown in late winter?
- Break a tip open: if it is hollow with frass inside, arborvitae leafminer is the likely cause; if not, suspect winter injury or disease.[1]
- Will arborvitae leafminer kill my hedge?
- Rarely; plants usually survive even heavy damage, though they can look bad and parasites often bring numbers down within a few years.[1][2]
Sources
- UMass Extension Landscape, Nursery and Urban Forestry Program, “Arborvitae Leafminer (fact sheet, R. Childs, rev. 10/2011).” www.umass.edu/agriculture-food-environment/landscape/fact-sheets/arborvitae-leafminer (accessed 2026-10-17)
- NC State Extension, “Arborvitae Leafminer (PDIC Factsheet).” content.ces.ncsu.edu/arborvitae-leafminer (accessed 2026-10-17)
- iNaturalist, “Argyresthia thuiella taxon page (order and family).” www.inaturalist.org/taxa/128555 (accessed 2026-10-06)