Ambermarked birch leafminer

Tunnel containing several larvae Thérèse Arcand

French common name: Tenthrède mineuse de Thomson
Scientific name: Profenusa thomsoni (Konow)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Tenthredinidae

Distribution

Canada

Damage, symptoms and biology

The presence of small, light-coloured blotches on the upper surface of leaves in July and the browning of the foliage later in the season are characteristic of attacks by the ambermarked birch leafminer. Depending on the severity of the damage to the foliage, the weakened tree may become more susceptible to other insects, but generally does not die from attack by this leafminer.

The ambermarked birch leafminer has only one generation each year. The eggs are laid inside the leaf. On hatching, the larvae begin mining the leaves, feeding on the interior tissue, causing them to turn brown. When fully grown, they leave the mines, drop to the ground and construct cocoons in which they overwinter.

Other information

Long known in Europe, the ambermarked birch leafminer is probably an introduced species and, until 1955, it was confused with the birch leafminer in Canada. First reported in Quebec in 1959, this insect occurs throughout Canada.

The ambermarked birch leafminer prefers shaded or semi-shaded foliage on small trees. Open-growing ornamental birches are generally less susceptible to attack by this species.

Large numbers of larvae in mined leaves result in a shortage of food, which quickly puts an end to an infestation. Because the damage occurs late in the season and because even a severe infestation seldom lasts more than one year, control measures are generally unnecessary.

Canadian Forest Service Publications

Ambermarked birch leafminer

Diet and feeding behaviour

Phyllophagous: Feeds on the leaves of plants.
- Miner: Feeds inside the blade of a leaf, between the epidermal layers, or beneath the bark of plants, by first excavating a mine into these tissues.