Forest Pests: Insects, Diseases & Other Damage Agents

Canadian Arborvitae Leafminer (Argyresthia canadensis)

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. Green body with dark brown head and with central brown patch on prothoracic shield and anal plate. Up to 7 mm.

Food. Northern white-cedar.

Life Cycle. One generation. Nearly full-grown caterpillar overwinters in mined foliage. Mature caterpillar present from April to June.

Comments. The caterpillars of the brown arborvitae leafminer, Coleotechnites thujaella, and three species of Argyresthia mine the foliage of northern white-cedar; sometimes several species will infest the same tree. As its name indicates, the brown arborvitae leafminer is brown, whereas the Argyresthia species are mostly green. Argyresthia aureoargentella and A. canadensis make whitish, spindle-shaped cocoons that are located outside the mine on the foliage. The cocoon of the first species is white, whereas that of the second is mottled with brown (see below). The arborvitae leafminer, A. thuiella, forms its pupa within its foliar mine.

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