Winter moth

Operophtera brumata

1. Identification

• Common name: Winter moth
• Scientific name: Operophtera brumata L.
• Order: Lepidoptera
• Family: Geometridae

2. Pest description

• Light-green caterpillars, with a faint dorsal line and a characteristic “looping” movement, reaching 20–25 mm.
• Winged males, brownish in colour, with a wingspan of 20–30 mm.
• Wingless or almost wingless females, unable to fly, remaining on the trunk or at the base of the branches.
• Defoliating species, active mainly in early spring.

3. Main hosts

• Apple.
• Pear, plum, cherry and other stone and pome fruits.
• Oak and other spontaneous broadleaf trees.

4. Symptoms and damage

• Early defoliation due to the feeding of the caterpillars on the young leaves.
• Irregular perforations and notches in the leaves.
• Reduction of tree vigour and decrease of the productive potential.
• More severe damage in cold and humid springs, which favour the development of the caterpillars.

5. Biological cycle

• Eggs laid in autumn, generally in bark cracks or near buds.
• Hatching in early spring, coinciding with bud burst.
• Caterpillars feed for 4–6 weeks.
• Pupation in the soil during the summer.
• Adults emerge in autumn; males fly, females move along the trunk for mating and egg-laying.

6. Monitoring

• Observation of caterpillars on the young leaves in early spring.
• Assessment of leaf damage in sensitive orchards.
• Pheromone traps for the detection of males in autumn.
• Counting of eggs on buds and branches during the winter.

7. Management measures

• Cultural: light tilling of the soil in summer to expose pupae; elimination of branches with a high concentration of eggs.
• Preventive: regular monitoring of bud burst and of the presence of caterpillars.
• Biological: application of Bacillus thuringiensis on young stages of the caterpillars.
• Integrated protection: definition of intervention thresholds, judicious use of authorised insecticides and integration with phenological monitoring.

Bibliographic references

• CABI – Invasive Species Compendium – Operophtera brumata.
• EPPO Global Database – Operophtera brumata.
• Carter, D. J. (1984). Pest Lepidoptera of Europe. Dr W. Junk Publishers.
• Alford, D. V. (2007). Pest and Disease Management Handbook. Blackwell Publishing.
• Tikkanen, O.‑P. et al. (2006). Phenology of the winter moth and host interactions. Oecologia, 147, 164–173.