River Birch Pink Residue: Leafminer Again

14-year-old river birch in Minnesota has pink residue on leaves and yellow-green striping. Both trees affected.

Diagnosis: Birch Leafminer

Sawfly larvae create blotch mines. "Pink residue" likely early mine coloration or frass. "Striping" = mining between veins.

Details

• Overwinter in soil.
• Adults emerge spring, lay eggs in new leaves.
• 2-3 generations/year.
• Heavy infestations cause browning, refoliation, growth loss.
• Weakens tree to bronze birch borer.

Resource

PSU Woody Plants fact sheet: detailed photos and control.

Systemic insecticide (acephate, imidacloprid) at first sign next spring.