Brown cedar leafminer

French common name: Mineuse rougeâtre du thuya
Scientific name: Coleotechnites thujaella (Kft)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Gelechiidae

Distribution

Eastern Canada

Eastern Canada and northeastern United States

Damage, symptoms and biology

The cedar leafminers are common pests of cedar in eastern Canada and the northeastern United States. These insects feed by tunneling inside the foliage at the tips of twigs causing the cedar leaflets to turn dull yellow.

The brown cedar leafminer adult moth is creamy white with heavy dustings of black and brown scales. The wingspan is about 9 mm. Eggs are laid from late June to early August on the scale-like leaves near the tip. Upon hatching the larvae bore into the leaves and feed as miners until the onset of winter. The full-grown larva is about 3 mm long; the body is reddish with dark legs and a black head, with a dark brown spot on the segment behind the head and on the last segment of the abdomen.

Larvae spend the winter in the mines. Pupation takes place in the spring within the mined leaflet. The pupae are brownish green and are pointed and curved at the tip. Both pupation and adult emergence occur a few weeks later than the arborvitae leafminer.

Other information

Four species of leafminer tunnel in the leaflets of cedar. It is not uncommon to find all four species at a single location. The two most commonly found cedar leafminers are the arborvitae leafminer, Argyresthia thuiella, and the brown cedar leafminer, Coleotechnites thujaella.

Canadian Forest Service Publications

Brown cedar leafminer

Diet and feeding behaviour

Phyllophagous: Feeds on the leaves of plants.
- Miner: Feeds inside the blade of a leaf, between the epidermal layers, or beneath the bark of plants, by first excavating a mine into these tissues.