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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 should be reported to the relevant plant health authority.
Citrus longhorn beetle adult and exit hole. Fera, ©Crown copyright, 2011
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.
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.
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.
Asian and citrus longhorn beetle larvae can cause serious damage to healthy trees, both in gardens and in the wider landscape.
Any findings must be reported to the relevant plant health authority, contact details can be found on the UK Plant Health Information Portal.
If either of these beetles is discovered, the relevant plant health authority 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.
Defra factsheet on Citrus longhorn beetle
Factsheet on differentiating Anoplophora longhorn beetle damage from that of native wood-boring insects invasive non-native species
Recording Invasive Species Count (RISC) survey
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