The citrus longhorn beetle, Anoplophora chinensis, has been identified at more than 14 locations across the UK, having been imported from China on Japanese maple plants via the Netherlands and distributed on mail-order plants.
A Defra representative could not reveal which mail-order firm was responsible but said the pest was found "mainly in private gardens".
A. chinensis is a large, black beetle with distinct white markings and long antennae, which has most commonly been found on bonsai trees such as maples and dwarf apples in the UK. But its host range also includes many shrubs and other trees such as beech, birch, horse chestnut and oak.
Citrus longhorn larvae feed inside plant stems and tree trunks, taking between one and three years to emerge as adults, so infestation is difficult to detect. Large exit holes in the trunk above or below ground level are left when adults emerge.
The pest is unlikely to establish in the UK according to a 2006 Defra report, which said it was "unlikely to establish outdoors" in the UK because summer temperatures are unlikely to be high enough for it.
If you see one of the distinctive beetles, isolate it in a sealed container and contact your local Plant Health & Seeds inspector via www.defra.gov.uk/planth/senior.htm or call 01904 455174.
- Symptoms to look out for are: sawdust-like "droppings" or wood pulp around holes and larval tunnels in the wood under loose or thin bark; large exit holes just above or below ground level; scraped sections of bark; chewed leaves and damage to the petioles by adults; and T-shaped egg slits in the bark.