PestMedium Severity

Birch Leaf Miner

Fenusa pusilla

A small sawfly whose larvae mine between the upper and lower leaf surfaces of birch trees, creating distinctive brown blotches. While healthy trees can tolerate infestations, repeated attacks over several years can significantly weaken trees.

Peak Season: Adults emerge in spring, multiple generations through growing season. Most damage visible in late spring and summer. Final generation overwinters in soil.
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Birch leaf miner damage showing characteristic leaf mining patterns and browning

Identification & Symptoms

What to Look For

Brown blotches or blisters on leaves from mining activity
Uniformly brown appearance of affected trees
Tree tops most severely affected
Mining tunnels visible when leaves held to light
Small, white, flattened larvae visible in mines
Black fecal matter in leaf mines
Premature leaf browning and drop
Reduced tree vigor with repeated infestations

Potential Damage

Reduced photosynthetic capacity from leaf mining
Aesthetic damage to landscape trees
Tree weakening with repeated infestations
Increased susceptibility to other pests
Predisposition to borer and fungal attacks
Premature defoliation in severe cases

Lifecycle

Adults emerge from soil in spring when birch leaves are half-developed. Females lay eggs in young leaf tissue. Eggs hatch in about a week, larvae feed for 10-15 days creating mines that often unite into large blotches. Larvae drop to ground, pupate in soil, and emerge for additional generations. 2-4 life cycles occur per year, with final generation overwintering in soil.

Professional Treatment Approach

1

Systemic insecticides in spring before egg laying

2

Soil treatment to target overwintering larvae

3

Maintain tree health and vigor

4

Remove fallen leaves to reduce overwintering sites

5

Monitor for early detection

6

Accept light damage on healthy trees

Recommended Mauget Products

Imisol (Imidacloprid)

Professional-grade treatment specifically effective against birch leaf miner.

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Imicide (Imidacloprid)

Professional-grade treatment specifically effective against birch leaf miner.

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Dinocide (Dinotefuran)

Professional-grade treatment specifically effective against birch leaf miner.

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Vigor-53 (Tree health support)

Professional-grade treatment specifically effective against birch leaf miner.

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