Apple fruit moth

Argyresthia conjugella

1. Identification

• Common name: Apple fruit moth
• Scientific name: Argyresthia conjugella Zeller
• Order: Lepidoptera
• Family: Yponomeutidae

2. Pest description

• Small caterpillars, cream-white to pinkish in colour, with a brown head.
• Very small adults (about 8–10 mm wingspan), with narrow forewings, brownish with pale markings and a marbled pattern.
• Narrow, fringed hindwings.
• Species associated above all with temperate-climate fruit trees, with a preference for apple and rowan.
• It attacks young fruits, penetrating through the calyx area or through micro-cracks in the skin.

3. Main hosts

• Apple tree.
• Wild rowan.
• Pear trees and other Rosaceae may be attacked occasionally.

4. Symptoms and damage

• Small, inconspicuous perforations in the skin of the fruits.
• Internal galleries filled with frass, leading to internal rotting.
• Premature drop of young fruits.
• Damage frequently confused with that of Cydia pomonella, but generally with more superficial galleries.
• In years of low wild-rowan production, the pest moves more intensely to apple orchards.

5. Biological cycle

• One generation per year in most regions.
• Eggs laid on the surface of the fruits or near the calyx.
• Caterpillars penetrate the fruit quickly after hatching.
• Pupation occurs outside the fruit, generally in cracks in the bark of the trees or in the leaf litter.
• Adults emerge in summer, synchronised with the development of the host fruits.

6. Monitoring

• Observation of initial perforations in young fruits.
• Sampling of fallen fruits for detection of galleries and caterpillars.
• Pheromone traps for detection and monitoring of flights.
• Assessment of the percentage of damaged fruits at different stages of development.

7. Management measures

• Cultural: removal of fallen fruits, destruction of infested fruits and maintenance of clean orchards.
• Preventive: choice of less susceptible varieties and balanced management of the fruit load.
• Biological: conservation of natural enemies and use of selective biological products.
• Integrated protection: monitoring with pheromones, definition of intervention thresholds and judicious application of authorised insecticides.

Bibliographic references

• CABI – Invasive Species Compendium – Argyresthia conjugella.
• EPPO Global Database – Argyresthia conjugella.
• Knudsen, G. K., & Bång, J. (2006). Monitoring and management of Argyresthia conjugella in apple orchards. Journal of Pest Science, 79, 33–40.
• Jaastad, G., et al. (2012). Biology and control of the apple fruit moth Argyresthia conjugella. Acta Agriculturae Scandinavica, 62, 1–10.