Birch Leafminer

Scientific Name: Fenusa pusilla

Birch leafminer is the larval stage of a small “fly-like” wasp. The larvae feed between the
epidermal layers of a leaf and thus are protected from predators and parasites by the leaf.
Once damage is obvious, it is usually too late to treat as the larvae leave the mine to pupate.
Control measures need to be systemic or be timed to coincide with early larval feeding before
damage becomes apparent.

Attacks: All birch species

What you will see:

• Large blotch mines in the leaves
• Damage is scattered throughout the tree
  • Mines will turn brown
  • Leaves will look wilted
• High populations can damage the entire canopy
• Repeated defoliation by leaf miner will decrease tree health
• Leaf miner defoliation is directly correlated to Bronze birch borer attack

Life cycle:

• Pupae overwinter in a cocoon 1-2 inches under the soil
• Adults emerge in Spring (April-May)
• Mated females lay eggs in leaf (May)
• Larvae produce a blotch mine (May-June)
• Larvae form a pupation chamber in the soil (June)

Cultural Management of Birchleaf Miner

Cultural practices:

• Water trees during dry season
  • Plant birch in shady, cool, moist areas
• Reduce fertilization
  • High nitrogen trees are more attractive to leafminers
  • Mulch with Prescription Organic Matter©
• Plant flowers to provide nectar sources for parasitic wasps

Chemical treatments are effective in controlling the birch leafminer. Please consult with your Arborist for treatment recommendations.