• Native to North America.
  • Birch skeletonizer is a small, native, leaf feeding insect.
  • Outbreaks seem to follow cyclical patterns and are relatively short in duration – 2-3 years normally.

Host species

The preferred host for this insect is white birch (Betula papyrifera), but it will feed on other species of birch.

Characteristics and life cycle

  • Birch skeletonizer spends the winter in tiny brown ribbed cocoons that it constructs in the litter under host trees.
  • The moths are small (wing span between 6-9 mm), brown in colour with white bands across their forewings, and hind wings that are grey and heavily fringed.
  • Moths emerge between early June and late July and lay their eggs singly and randomly on either the upper or lower surface of host leaves.
  • Approximately 2 weeks after egg laying, the tiny white larvae emerge by boring through the bottom surface of the egg and begin mining the interior tissue of the leaf.
  • After 3 to 4 weeks, translucent yellow/green larvae emerge from the interior and begin to consume the lower surface of the affected leaves giving the leaf a transparent appearance.
  • The larvae subsequently go through two molts under tiny “felt-like” mats on the leaf surface; they develop brown heads and functional legs throughout these molts.
  • The mature larvae, which are approximately 6 mm long, drop to the ground and spin their overwintering cocoons in the leaf litter.

Birch skeletonizer larva

Symptoms and damage

  • Orange/brown birch foliage in mid-August; freshly consumed leaves have a transparent appearance with small white silken pads (molting pads) on leaf surfaces.
  • Trees weakened after repeated defoliation that can become susceptible to other more harmful vectors (example Bronze birch borer, Agrilus anxius).
  • During heavy infestation, thousands of larvae can be found billowing out on silken threads from affected trees on windy days.

Birch skeletonizer damage

Control measures

To date, no large-scale controls have been initiated as the late season feeding habits of this insect causes minimal damage to the tree. For ornamentals, infection can be reduced through the removal of litter from under affected trees.