European oak leafroller – Tortrix viridana

Background

The European oak leafroller (Tortrix viridana) is a defoliator of hardwood trees and shrubs, stripping these trees and shrubs of its leaves. It is a pest of potential concern that is not known to occur in Canada and that is not on the regulated pest list. However, early detection could facilitate the management of this green moth. The European oak leafroller can be distinguished from all other native and naturalized moths in Canada by its green bell shape. If you believe you have found suspect specimens, please contact the Canadian Food Inspection Agency (CFIA).

Plant Pest Credit Card- European oak leafroller PDF (1.0 mb)

Identification

Adult: front wings are pale-green or yellow-green; rear wings are brownish-gray to grayish; both wings have a white, frayed outer edge.Footnote 1 Footnote 3 Footnote 4 Footnote 9 The wingspan is approximately 18 to 23 mm.Footnote 1 Footnote 4 Footnote 9 The head is yellowish and adults have a grayish, 8 mm long abdomen.Footnote 1 Footnote 4

Larva: Younger larvae are gray coloured with dark heads.Footnote 1 Older instar larvae turn gray-green.Footnote 6 Larvae are 15 to 19 mm long and 2.5 mm wide.Footnote 4

Egg: Eggs are round, with a diameter of about 0.7 mm.Footnote 1 Footnote 4 They are initially light yellow, later changing to brown.Footnote 1 Footnote 4

Hosts

Hosts include Oak [Quercus (main host)], maple (Acer), birch (Betula), hornbeam (Carpinus), beech (Fagus) and poplar (Populus).Footnote 1 Footnote 4 This leafroller also feeds on shrubs including Vaccinium and Urtica.

Location of Infestation Within Tree

Larvae feed on foliage, with the most preferable section being the upper crown.Footnote 1

Host Condition

Drought stressed and healthy hosts. Pole-sized trees and older trees are preferred.Footnote 1

Distribution

This insect is known to occur in Europe, northern Africa, Cyprus, Iran and Israel.Footnote 1 Footnote 3 Footnote 4 Footnote 8

Signs and Symptoms

Each female lays approximately 50 to 60 eggs in pairs within a cement-like mass.Footnote 4 Footnote 5 Footnote 9 Eggs are deposited on branches, leaves, and branch forks, within the entire crown.Footnote 1 A dust and algae lining make the eggs nearly invisible.Footnote 1 Emerging larvae bore into open buds, since closed buds cannot be penetrated.Footnote 1 Therefore, emerging larvae can only survive if the buds are in synchrony with their development.Footnote 1 As the buds flush, the larvae move to young leaves and flowers and continue feeding.Footnote 1 Footnote 4 Larvae construct shelters by rolling leaves with silk webbing.Footnote 4 Third instar larvae become more mobile and are thus more visible. Similar to other tortricids, when larvae are disturbed, they will drop on a silken thread.Footnote 2 Last instar larvae feed upon the expanded foliage as well as the bark of tender young shoots.Footnote 4 Footnote 5

Tortrix viridana is part of a Quercus dieback complex that results in thinning foliage, progressive die-back, cambial necrosis, epicormic shoot development and tree mortality.Footnote 6 Footnote 7 Footnote 8 Successive defoliation can cause growth loss and can also weaken trees and predispose them to mortality by other organisms.Footnote 4

Adult T. viridana

A. Adult T. viridana (18-23 mm wingspan). Note pale-green forewings and frayed outer edge.

Gray-green T. viridana larva

B. Gray-green T. viridana larva (late instar).

T. viridana larva

C. T. viridana larva (15-19 mm long).

Rolled leaf shelters created by T. viridana larvae

D. Rolled leaf shelters created by T. viridana larvae.

Thinned crowns caused by T. viridana defoliation

E. Thinned crowns caused by T. viridana defoliation.

Rolled leaf shelters created by T. viridana larvae

F. Rolled leaf shelters created by T. viridana larvae.

Photo Credits

  1. Berks, www.bioimages.org.uk
  2. Hannes Lemme, Sächsische Landesanstalt für Forsten, Image 1220075, www.forestryimages.org, March 5, 2004
  3. Gyorgy Csoka, Hungary Forest Research Institute
  4. Stephen Dalton, NHPA, Image SDA000721A, www.nhpa.co.uk
  5. Hannes Lemme, Sächsische Landesanstalt für Forsten, Image 1260040, www.forestryimages.org, June 5, 2004
  6. Gyorgy Csoka, Hungary Forest Research Institute
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