Orchard ermine moth

Yponomeuta padella

1. Identification

• Common name: Orchard ermine moth
• Scientific name: Yponomeuta padella L. 
• Synonym: Hyponomeuta padella L.
• Order: Lepidoptera
• Family: Yponomeutidae

2. Pest description

• Whitish caterpillars with black dots, highly gregarious.
• They form dense webs that envelop leaves and branches.
• White adults with small black spots, of typical “ermine” appearance.
• They attack mainly young leaves, possibly causing significant defoliation.
• Species common on pome fruits and wild rosaceous plants.

3. Main hosts

• Plum tree.
• Peach tree.
• Apple tree.
• Pear tree.
• Common hawthorn (Crataegus monogyna).
• Blackthorn (Prunus spinosa).
• Other shrubby and arboreal rosaceous plants.

4. Symptoms and damage

• Dense webs enveloping leaves, shoots and branches.
• Total consumption of the leaf blade within the webs.
• Partial or severe defoliation in intense attacks.
• Reduction in vigor and annual growth.
• Greater susceptibility to other pests and diseases.

5. Biological cycle

• One generation per year.
• Eggs laid in batches on branches in summer.
• Caterpillars overwinter inside the eggs (L1 stage).
• They resume activity in spring, forming webs and feeding in groups.
• Pupation inside the webs.
• Adults emerge in early summer.

6. Monitoring

• Observation of webs and gregarious caterpillars in spring.
• Checking for egg batches on the branches in late summer.
• Assessment of defoliation intensity.
• Recording the pest's progression over the years.

7. Management measures

• Cultural: removal and destruction of webs and heavily attacked branches, improved canopy ventilation and maintenance of tree vigor.
• Biological: conservation of natural enemies, including egg and larva parasitoids.
• Integrated protection: interventions only when justified, judicious application of authorized insecticides and integration of cultural practices to reduce pest incidence.

Bibliographic references

• EPPO Global Database – Yponomeuta padella.
• CABI Invasive Species Compendium – Y. padella.
• Alford, D. (2007). Pest management in fruit crops.
• Leather, S. R. (2018). Ecology of insect pests of temperate fruit trees. Annual Review of Entomology.
• Powell, J. A. (1992). Lepidoptera of Europe: Yponomeutidae biology and systematics.