Elm leaf beetle

Pyrrhalta (=Xanthogaleruca) luteola

1. Identification

• Common name: Elm leaf beetle
• Scientific name: Pyrrhalta luteola Müller
• Synonym: Xanthogaleruca luteola Müller; Galeruca xanthomelaena Schr.
• Order: Coleoptera
• Family: Chrysomelidae

2. Pest description

• Adults: Small leaf beetles of 6–7 mm; yellowish-green body; elytra with faint dark longitudinal lines; activity most intense during the summer.
• Larvae: Elongated body, yellowish to greenish, with small dark spots; feed intensively on the underside of the leaves.
• Pupae: Develop in the soil, in small earthen chambers.
• Eggs: Laid in groups on the underside of the leaves.

3. Main hosts

• Elms (Ulmus minor, Ulmus glabra, Ulmus laevis).
• May occur in other species of the genus Ulmus, especially in urban and ornamental trees.

4. Symptoms and damage

• Leaves with scraped or skeletonised areas due to larval feeding.
• Borings and loss of leaf tissue caused by the adults.
• Partial or total defoliation in severe attacks.
• General weakening of the tree, making it more susceptible to other pests and diseases, including Dutch elm disease.
• Reduction of ornamental value in urban avenue trees.

5. Biological cycle

• Two to three generations per year, depending on temperature.
• Adults emerge in spring and begin egg-laying on the underside of the leaves.
• Larvae feed intensively before falling to the ground for pupation.
• Adults of the last generation overwinter in natural shelters or in the leaf litter.
• Development favoured by hot, dry summers.

6. Monitoring

• Observation of scrapings and borings on the young leaves.
• Inspection of the underside of the leaves to detect eggs and larvae.
• Assessment of defoliation intensity throughout the crown.
• Reinforced monitoring in urban trees and in locations with a history of the pest.

7. Management measures

• Cultural: Removal of fallen leaves to reduce overwintering sites; promotion of tree vigour through adequate watering and fertilisation.
• Preventive: Selection of less susceptible elm species or varieties; regular sanitary maintenance.
• Integrated protection: Intervention only when population levels justify it; preference for selective methods compatible with beneficial organisms; continuous monitoring in urban areas.

Bibliographic references

• CABI Invasive Species Compendium – Pyrrhalta luteola.
• EPPO Global Database – Xanthogaleruca luteola.
• Solomon, J. D. (1995). Guide to insect pests of ornamental trees.
• Lieutier, F., et al. (2004). Bark and wood boring insects in living trees in Europe.