Apple leaf miner

Lyonetia clerkella

1. Identification

• Common name: Apple leaf miner
• Scientific name: Lyonetia clerkella L.
• Order: Lepidoptera
• Family: Lyonetiidae

2. Pest description

• Adults: small moths with a 6–8 mm wingspan; narrow forewings, white with silvery reflections and a dark spot at the tip; grey, heavily fringed hindwings.
• Larvae: very small, yellowish-green in colour; they produce long, sinuous mines, usually on the upper side of the leaves.
• Pupae: form on the outside of the mine, usually in a white silken cocoon, often suspended from the leaf by silk threads.
• Eggs: laid singly on the surface of the leaf, mainly on the upper side.

3. Main hosts

• Pomoideae: apple tree, pear tree.
• Ornamental and spontaneous species: birch, cherry tree, plum tree, hawthorn.
• Other Rosaceae and deciduous trees may be affected.

4. Symptoms and damage

• Long, narrow and sinuous mines, often very visible on the upper side.
• The mines become progressively wider as the larva grows.
• Translucent or silvery areas on the leaves.
• Perforations and partial drying of the mined tissue.
• In intense attacks, reduction of the photosynthetic area and premature leaf drop.
• Possible reduction of plant vigour, especially in young trees.

5. Biological cycle

• Two to four generations per year, depending on climatic conditions.
• Eggs laid in spring; larvae quickly begin the formation of the mine.
• Larval development with several instars inside the mine.
• Pupation usually on the outside of the mine, in a suspended silken cocoon.
• Adults emerge throughout spring and summer, with variable flight peaks.
• Overwintering normally as a pupa.

6. Monitoring

• Direct observation of recent sinuous mines on the leaves.
• Counting mined leaves on representative branches.
• Pheromone traps for detection and tracking of adult flights.
• Assessment of the intensity of defoliation and the evolution of the mines throughout the season.

7. Management measures

• Cultural: removal and destruction of heavily attacked leaves; collection of fallen leaves in autumn; maintenance of airy canopies to reduce pest pressure.
• Biological: promotion of natural parasitoids (e.g.: Pnigalio spp., Sympiesis spp., Chrysocharis spp.) that attack larvae and pupae.
• Integrated protection: regular monitoring, intervention only when attack levels justify it; application of measures that reduce the survival of larvae inside the mines.

Bibliographic references

• EPPO Global Database – Lyonetia clerkella.
• CABI Invasive Species Compendium – Lyonetia clerkella.
• Alford, D. V. (2007). Pest and Disease Management Handbook. Blackwell Publishing.
• Emmet, A. M. (1985). A review of British Lyonetiidae. Journal of Natural History.
• Johansson, R., Nielsen, E. S., Nieukerken, E. J. van, & Gustafsson, B. (1990). The Nepticulidae and Opostegidae of North-West Europe.