Other Common Names
Thuja Mining Moth
American Thuja Shoot Moth
Synonyms and other taxonomic changes
Argyresthia thuiella (Packard, 1871)
Bucculatrix thuiella Packard, 1871
* phylogenetic sequence #077275
Explanation of Names
Named derived from the genus of its primary host (Thuja).
Identification
Adult - forewing pale gray or whitish with 3 dark gray or black patches along inner margin (creating a 3-banded effect when wings are held together at rest); 4 or 5 small dark marks present along costa near apex.
Larva - body reddish-green to brownish-green; head black.
Range
Southeastern Canada and northeastern US to North Carolina, west to Missouri, north to Manitoba (plus disjunct population in British Columbia). Also occurs in Europe.
Season
Adults fly from late May to July.
Larvae year-round in leaves of host.
Food
Larvae are leaf miners, feeding mainly on
arborvitae, a.k.a. northern white-cedar, (
Thuja occidentalis) plus other arborvitae and false cypress (
Chamaecyparis spp.).
(2),
(1)Life Cycle
One generation per year; overwinters as a dormant larva inside leaves of host plant; larvae resume feeding in the spring by extending their mines toward the interior of the crown, then pupate from March to May (in the south) or May and June (in the north), emerging as adults from late May to July; eggs are laid in June and July; newly-hatched larvae mine into the foliage and continue to feed into fall, causing the leaves to turn brown.
Remarks
First reported in the US in Connecticut (1921), and first reported in Canada in Ontario (1940). Severe attacks over several consecutive years can kill twigs and stems but infested trees are usually able to renew their foliage later during the growth season.
In June and July, a close approach to infested trees causes the adults to briefly fly up in a cloud, then settle again within a minute on the host trees or nearby vegetation.
At least 26 species of parasitoids have been reported in US and Canada, including the encyrtid wasp Litomastix (Pentacnemus) bucculatricis and the braconid wasp Pholetesor (Apanteles) bedelliae.
Print References
Busck, A. 1907. Revision of the American moths of the genus
Argyresthia. Proceedings of the United States National Museum 32:
23-24 (1)
Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, R.C. Reardon 2011. Caterpillars on the Foliage of Conifers in the Northeastern United States (Revised). USDA FHTET-2011-07: 21 (
20Mb PDF)
(2)Internet References
pinned adult and live larva images plus photos of damage and description, biology, etc. (Diseases and Pests of Trees in Urban Environments, Austria)
drawings of all life stages plus description, biology, damage etc. (North Carolina State U.)
UMassAmherst - species page
