A spokesman for the Fera plant health team said the beetles naturally surface in June and are at their most active in July and August, making it the best time of year to identify their presence.
The beetle is a non-native pest than can be extremely damaging to a wide range of broad leaved trees and shrubs and is most commonly found on Japanese Maples originally imported from China.
A Fera statement said: "In other European member states outbreaks have already led to the destruction of thousands of mature trees and eradication costs running into millions of Euros. Although there are no known outbreaks of the citrus longhorn beetle in the UK, there have been several interceptions since 2005 as well as the widespread distribution of potentially infested plants by mail order in 2008, with several findings of the beetle since then.
"The outbreaks in Europe and findings in the UK demonstrate that the threat from the beetle is real. An outbreak in the Boskoop area of the Netherlands in 2009/2010 was of particular concern as there is a high concentration of nurseries there supplying trees and shrubs to the rest of Europe.
"This is why we are urging the industry and members of the public to be vigilant and to keep a look out for the pest.
"Adult beetles are large and black with variable white markings. Particularly distinctive are their antennae, which are longer than their bodies (between 1.2-2 times body length) and are black with white/light blue bands. The larval stage of the beetles is the most damaging. The larvae feed internally on the pith and vascular systems of the lower trunk and root. The tunnels created by the feeding leave trees susceptible to diseases and wind damage. The adults can cause more limited damage by feeding on foliage and eating young bark."
For further information on symptoms and identifying the pest visit the Fera website.
If you suspect the presence of this pest or see a beetle that you suspect to be a citrus longhorn beetle, trap it if possible, and immediately report the finding to your local Fera Plant Health and Seeds Inspector by phoning 01904 465625 or emailing firstname.lastname@example.org.
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