Elm Bark Beetle

Scolytus multistriatus

1. Identification

• Common name: Smaller European elm bark beetle
• Scientific name: Scolytus multistriatus Marsham
• Order: Coleoptera
• Family: Curculionidae (subfamily Scolytinae)

2. Pest description

• Adults: Small bark beetles of 2–3.5 mm; cylindrical dark brown body; elytra with multiple longitudinal striations; head partially hidden when viewed from above.
• Larvae: Legless, whitish, curved body, brown head; develop in galleries beneath the bark.
• Pupae: Whitish, formed in pupal chambers inside the bark.
• Galleries: Typical system with a short nuptial gallery and well-defined radial larval galleries.

3. Main hosts

• Elms (Ulmus minor, Ulmus glabra, Ulmus laevis).
• Preferentially attacks weakened trees, recently pruned, affected by drought or with mechanical damage.

4. Symptoms and damage

• Borings in the bark with expulsion of fine frass.
• Subcortical galleries that interrupt the flow of sap.
• Drying of branches and progressive decline of the crown.
• Yellowing and premature drop of the leaves.
• Important vector of Dutch elm disease  (a serious vascular disease caused by fungi of the genus Ophiostoma, which has caused the progressive decline and death of elms throughout Europe).

5. Biological cycle

• Two to three generations per year, depending on temperature.
• Adults emerge in spring and begin excavating egg-laying galleries.
• Eggs laid in the nuptial gallery; larvae excavate radial galleries.
• Pupation beneath the bark; new adults emerge and may start new generations.
• Development favoured by weakened trees, freshly cut wood and periods of drought.

6. Monitoring

• Observation of recent borings and expulsion of frass.
• Inspection of dry branches or those with symptoms of decline.
• Assessment of galleries beneath the bark on suspect trees.
• Reinforced monitoring after pruning, storms or periods of water stress.
• Use of pheromone traps for detection and population tracking.

7. Management measures

• Cultural: Removal and destruction of infested branches; elimination of cut wood; avoiding pruning during flight periods.
• Preventive: Maintenance of tree vitality; avoiding wounds to the bark; proper management of woody residues.
• Integrated protection: Use of pheromone traps for monitoring; intervention only when necessary; practices that reduce the attractiveness of fresh wood.

Bibliographic references

• CABI Invasive Species Compendium – Scolytus multistriatus.
• EPPO Global Database – Scolytus multistriatus.
• Stipes, R. J., & Campana, R. J. (1981). Compendium of Elm Diseases.
• Lieutier, F., et al. (2004). Bark and wood boring insects in living trees in Europe.