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First outbreak of dangerous tree pest found in UK

24/04/2012

An outbreak of the Asian longhorn beetle (ALB), an exotic beetle pest which could have severe consequences for British trees, has been found in Kent, the Food & Environment Research Agency (Fera) has confirmed.

Several larvae of the beetle were found inside a Poplar tree during a routine survey by the Forestry Commission at a site in the Paddock Wood area. It is thought the beetles originated from wood packaging used to import stone from China at an adjacent industrial site. This is the first evidence of tree infestation in the UK.

The Asian longhorn beetle is not native to the UK, and poses a serious threat to a wide range of broadleaved trees and shrubs such as Maple (including Sycamore), Elm, Horse Chestnut, Willow, Poplar, Birch and some fruit trees.

Adult beetles are large (about 20 - 40 mm long) and shiny black with variable white markings. Their antennae are particularly distinctive, being much longer than their bodies (up to twice the body length) and are black with white or light blue bands. The larvae of the beetle feed undetected on the inside of the plant, and can kill it or leave it weakened and susceptible to further pest and disease damage.

The adult beetles scrape away a portion of bark on a host tree to lay their eggs just underneath. The lifecycle from egg to beetle is one to two years in Asia, and possibly longer in the UK.  Beetles emerge from spring onwards and will mate and lay eggs, after which they die. When the larvae hatch, they feed by boring into the upper part of the trunk and branches, which makes them difficult to detect.

The most obvious symptoms of ALB damage are the circular adult exit holes, which are about 10 mm in diameter and are generally found in the main trunk and above. The adult beetles usually emerge from these holes between May and October.

Other signs of the beetle's presence which might be present but less obvious, include piles of sawdust-like droppings at the base of infested trees, scraped bark, and bleeding sap at the site where eggs have been laid.

Not only do the larvae cause structural damage, this damage also leaves the tree susceptible to other pests and diseases. This can eventually lead to the death of the tree.
Analysis of climate data by Fera scientists suggests that most of England and Wales and some warmer coastal areas of Scotland are suitable for ALB establishment, but south-east England and the south coast are at the greatest risk.

First outbreak of dangerous tree pest found in UK