Spotted tentiform leafminer

Phyllonorycter blancardella

1. Identification

• Common name: Spotted tentiform leaf miner of apple
• Scientific name: Phyllonorycter blancardella Fabricius
• Order: Lepidoptera
• Family: Gracillariidae

2. Pest description

• Adults: small moths with a 6–8 mm wingspan; narrow forewings, with silvery-white and golden-brown patterns; grey, fringed hindwings.
• Larvae: initially serpentine miners, later becoming blotch miners; yellowish-green body, very small.
• Pupae: develop inside the mine, protected by a silken cocoon, usually visible as a more opaque area.
• Eggs: laid singly on the underside of the leaf, near the veins.

3. Main hosts

• Apple tree.
• Pear tree.
• Hawthorn.
• Other arboreal Rosaceae may occasionally be affected.

4. Symptoms and damage

• Mines initially narrow and serpentine, evolving into larger, blotch-shaped mines, usually on the underside.
• Characteristic marbled appearance due to the contraction of the mined tissues.
• Translucent or silvery areas on the leaves.
• Curling of the leaf due to larval activity.
• In intense attacks, reduction of photosynthetic capacity and premature leaf drop.
• Possible reduction of plant vigour and impact on production.

5. Biological cycle

• Two to three generations per year, depending on climatic conditions.
• Eggs laid in spring; larvae quickly penetrate the leaf mesophyll.
• Larval development with several instars inside the mine.
• Pupation inside the mine, usually protected by a cocoon.
• Adults emerge throughout spring and summer, with variable flight peaks.
• Overwintering generally as a pupa inside the mine.

6. Monitoring

• Direct observation of recent mines on the underside of the leaves.
• Counting mined leaves on representative branches.
• Specific pheromone traps for detection and tracking of 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.) 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 – Phyllonorycter blancardella.
• CABI Invasive Species Compendium – Phyllonorycter blancardella.
• Alford, D. V. (2007). Pest and Disease Management Handbook. Blackwell Publishing.
• Blommers, L. H. M. (1994). Integrated pest management in European apple orchards.
• Emmet, A. M. (1985). A review of British Phyllonorycter species. Journal of Natural History.