Phoracantha or eucalyptus borer

Phoracantha semipunctata and Phoracantha recurva

1. Identification

• Common name: Eucalyptus longhorn, eucalyptus borer
• Scientific name: Phoracantha semipunctata Fabricius and Phoracantha recurva Newman
• Order: Coleoptera
• Family: Cerambycidae

2. Description of the pest

• Adults: Longhorn beetles of 15–25 mm, elongated body, brown coloration with light spots on the elytra; long antennae, typical of cerambycids; activity mainly at dusk and during the night.
• Larvae: White, cylindrical, with a brown head; they excavate extensive galleries in the cambium and surface wood, interrupting the flow of sap.
• Pupae: Formed inside the wood, in oval pupal chambers.
• Eggs: Deposited in bark cracks, preferentially in weakened or recently cut trees.

3. Main hosts

• Eucalyptus, especially Eucalyptus globulus and Eucalyptus camaldulensis, but they may attack other species of the genus Eucalyptus.
• A preference for weakened, recently felled, burnt trees, subject to water stress or with mechanical damage.

4. Symptoms and damage

• Oval emergence holes in the bark and expulsion of sawdust.
• Extensive galleries under the bark, causing cambial necrosis and interruption of the flow of sap.
• Drying of branches and crown, loss of vigour and yellowing of the leaves.
• Longitudinal cracks in the bark due to larval activity.
• In severe attacks, they may cause rapid decline and death of the tree, especially in young or weakened stands.
• Significant damage to cut wood, reducing its commercial value.

5. Biological cycle

• One to two generations per year, depending on the temperature.
• Adults emerge in spring and summer, being attracted to weakened trees or fresh wood.
• Egg-laying in bark cracks; larvae develop over several weeks, excavating extensive galleries.
• Pupation inside the wood; adults emerge through oval holes.
• Development favoured by high temperatures, prolonged droughts and an abundance of fresh or weakened wood.

6. Monitoring

• Observation of oval emergence holes and expulsion of sawdust.
• Inspection of trunks and branches to detect subcortical galleries.
• Evaluation of the crown for signs of drying or loss of vigour.
• Reinforced monitoring after cuts, storms, fires or periods of water stress.
• Light traps may be used to detect adults.

7. Management measures

• Cultural: Removal and destruction of infested wood; rapid debarking of cut wood; avoid prolonged storage of fresh wood; improvement of the vitality of the stands.
• Preventive: Reduction of water stress; avoid injuries to the trunk; appropriate density management; avoid cuts during periods of greater adult activity.
• Integrated protection: Regular monitoring; intervention only when necessary; practices that reduce the attractiveness of weakened trees; attention to the legal framework, given that Phoracantha spp. are considered relevant non-native pests in the European Union and appear on phytosanitary surveillance lists under Regulation (EU) 2016/2031 and Implementing Regulation (EU) 2019/2072.

Bibliographic references

• EPPO Global Database – Phoracantha semipunctata and Phoracantha recurva.
• CABI Invasive Species Compendium – Phoracantha spp.
• European Commission – Regulation (EU) 2016/2031 on protection against quarantine pests.
• European Commission – Implementing Regulation (EU) 2019/2072.
• Paine, T. D. et al. (1995). Biology and management of Phoracantha spp. in eucalyptus plantations.