Species Argyresthia thuiella - Arborvitae Leafminer - Hodges#2481

2481

Thuja Mining Moth

American Thuja Shoot Moth

Adult: wingspan about 8 mm

Larva: mature length 3-7 mm

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

southeastern Canada and northeastern US to North Carolina, west to Missouri, north to Manitoba (plus disjunct population in British Columbia)

also occurs in Europe

on leaves of host plant (mainly Eastern White Cedar)

adults fly from late May to July

larvae year-round in leaves of host

larvae are leaf miners, feeding mainly on Eastern White Cedar (Thuja occidentalis) plus other Arborvitae and False Cypress (Chamaecyparis spp.)

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

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.

pinned adult and live larva images plus photos of damage and description, biology, etc. (Canadian Forest Service)

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.)

larva and damage photos plus biology and control (U. of Guelph, Ontario)