European Oak Leafroller

Tortrix viridana

1. Identification

• Common name: Green oak tortrix, green oak leaf roller
• Scientific name: Tortrix viridana L.
• Order: Lepidoptera
• Family: Tortricidae

2. Pest description

• Adults: Small moths (≈ 18–22 mm wingspan); bright green forewings with pale margins; brownish hindwings.
• Larvae: Light green caterpillars, very similar to the colour of the leaves; brown head; up to 18–20 mm long; live rolled up in the leaves.
• Eggs: Laid in plates on the bark of the thin branches, usually in summer.

3. Main hosts

• Holm oak.
• Cork oak.
• Portuguese oak.
• Other Mediterranean oaks.

4. Symptoms and damage

• Leaves rolled up and joined by silk threads.
• Intense consumption of the leaf blade, leaving veins exposed.
• Partial or total defoliation in severe attacks.
• Reduction in the vigour of the tree, lower annual growth and greater susceptibility to other biotic and abiotic agents.

5. Biological cycle

• Winter spent as an egg on the bark of the branches.
• Hatching in spring, coinciding with the budburst of the oaks.
• Larvae feed on the young leaves, remaining inside rolled-up leaves.
• Pupation inside the leaves or in the canopy.
• Adults emerge in early summer.
• One generation per year.

6. Monitoring

• Observation of rolled-up leaves and the presence of caterpillars in spring.
• Assessment of the degree of defoliation in the canopy.
• Search for egg plates on the thin branches at the end of summer.
• Annual monitoring with pheromone traps in sensitive montados and oak woodlands.

7. Management measures

• Cultural: Promotion of tree vigour; reduction of water stress; appropriate management of the montado.
• Biological: Conservation of natural enemies (parasitoids of eggs and larvae, insectivorous birds).
• Integrated protection: Annual monitoring; intervention only when defoliation is significant; chemical treatments rarely recommended owing to the environmental impact and the difficulty of covering the canopy.

Bibliographic references

• EPPO Global Database – Tortrix viridana.
• CABI Invasive Species Compendium – Tortrix viridana.
• Barbosa, P. et al. (2010). Defoliating insects in Mediterranean oak systems.
• Villemant, C. (2001). Biology and ecology of Tortrix viridana.