Citrus and Asian longhorn beetles

Citrus longhorn beetle, Anoplophora chinensis, and Asian longhorn beetle, Anoplophora glabripennis, are non-native wood-boring pests that can cause serious damage to a wide range of broad-leaved trees and shrubs. Citrus longhorn beetles have been intercepted in the UK on imported Japanese maples.  An outbreak of Asian longhorn beetle at Paddock Wood, Kent in 2012 is believed to have been eradicated. These beetles are not yet established in the UK and are quarantine pests in the European Union. Any sightings in Britain must be reported to the Food and Environmental Research Agency (FERA).

Citrus longhorn beetle adult and exit hole. Fera, ©Crown copyright, 2011

Quick facts

Common names Citrus longhorn beetle; Asian longhorn beetle
Scientific names Anoplophora chinensisAnoplophora glabripennis
Plants affected Acer spp, birch, hazel, citrus, apple and many other deciduous trees and shrubs
Main symptoms Large (6-11mm diameter) exit holes in the branches, trunk, stem base and exposed roots
Most active Adult beetles: July-August. Larvae: all year round

What are citrus and Asian longhorn beetles?

Asian and citrus longhorn beetles have larvae that feed within the trunks, branches and larger roots of a wide range of deciduous trees and shrubs. The tunnels created by the larvae can cause substantial damage to healthy trees. They are native to China, Japan and other countries in south-east Asia. Citrus longhorn beetles have been moved around the world in ornamental trees imported from Asia, especially in Japanese maples from China. The main entry route for Asian longhorn beetle has been in timber used for pallets and wooden packing cases sent with goods imported from east Asia. These beetles pose a serious threat to horticulture, forestry and native trees in the UK.

Symptoms

Gardeners are likely to become aware of the presence of these longhorn beetle either when they notice the adult beetle or find exit holes near the base of infested trunks or exposed roots with citrus longhorn, while exit holes of Asian longhorn can be much higher up a tree in the trunk or branches.

  • Citrus longhorn beetle is a large (21-37mm long) black beetle with white markings on its wing cases
  • The antennae are particularly distinctive because they are up to twice the length of the body and are black with white/light-blue bands
  • The Asian longhorn beetle is very similar in size and appearance 
  • Some non-pest native longhorn beetles have banded antennae but they are not black with white spots
  • The legless larvae are creamy white with pale brown heads and are up to 56mm long

The larvae of citrus longhorn beetle make tunnels in the lower trunk and roots of host plants for two years or more. There may be no external signs of infestation until the adult beetle emerges, leaving a circular exit hole 6-11mm in diameter. These are typically found near the base of trunks or on exposed roots. Larvae of Asian longhorn beetle develop higher up in the trunks and branches of many deciduous trees. The tunnels created by the larval feeding make trees susceptible to diseases and wind damage. The adults cause limited damage by eating foliage and young bark.

The problem

Asian and  citrus longhorn beetle larvae can cause serious damage to healthy trees, both in gardens and in the wider landscape.

The Food and Environmental Research Agency (FERA) requires anyone finding this pest to let them know by contacting them directly. Tel. 01904 465625 or email planthealth.info@fera.gsi.gov.uk. Alternatively, fill in the survey form.

Control

If either of these beetles is discovered, FERA will advise what steps must be taken to deal with the infestation. They are difficult to control because the larvae and pupae are concealed and protected within the trunk, branches or larger roots. Currently, the only effective way of controlling larvae is to fell infested trees and destroy the pest by chipping, burning or deeply burying the infested trunks and roots.

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