Forest Pests: Insects, Diseases & Other Damage Agents

Brown Arborvitae Leafminer (Coleotechnites thujaella)

Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p.

Description. Brown body with dark brown head, prothoracic shield, and anal plate. Prothoracic shield with light brown anterior margin; narrow, light brown band at hind margin of segments. Up to 8 mm.

Food. Northern white-cedar.

Life Cycle. One generation. Partly grown caterpillar overwinters in its mine. Mature caterpillar present from May to July.

Comments. The brown arborvitae leafminer lives its entire life in a mine that turns dark brown (and later fades to light brown) after the inner tissue has been removed. After feeding is completed, it forms a brown pupa within the mine. This caterpillar is the only brown one that mines northern white-cedar (arborvitae). Several greenish Argyresthia species also infest arborvitae; see the comments for the Canadian arborvitae leafminer, A. canadensis. The brown arborvitae leafminer is one of the most important pests of arborvitae in the Northeast.

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