Invasive Species

Invasive Weeds
Invasive weeds are plant species that take over habitats, decreasing their wildlife value and eradicating native plant species. If allowed to grow unchecked, they can destroy the characteristic Chilterns natural landscapes.
In Chesham, three plants are known to be invading the area:
Invasive Animals
Harlequin ladybird taken in Chesham during 2007The most invasive ladybird in the world, the Harlequin Ladybird, has arrived in Chesham. Originally from East Asia, this ladybird was accidentally introduced to the UK in 2004 and has been spotted in Chesham.
The Harlequin has a big appetite, eating a wide range of foods, including butterflies, moths and other ladybirds – which means that the Harlequin could endanger native insects.
A survey has been set up to follow the Harlequin’s spread across the UK and we would like you to report your Chesham sightings. For information on how to identify this highly variable ladybird or to report a sighting, go to
Citrus Longhorn Beetle
DEFRA is warning gardeners to be on the look-out for this beetle, originally from South East Asia. The beetle has been found in nurseries and private gardens in the UK and is a pest of a range of trees and shrubs, especially maples. However, the Citrus Longhorn Beetle also attacks beech, birch, hawthorn, hazel, horse chestnut, plane, poplar, oak and willow. Download a factsheet from FERA to discover more (1.7 MB)  
The spread of American Mink in the River Chess catchment contributed to a dramatic population crash of the native water vole, as mink are voracious predators. The Chilterns Chalk Streams Project and BBOWT implemented a successful water vole recovery project, which included trapping and controlling mink on the river. Mink are still being monitored for along the length of the river to ensure that a population does not re-establish. People are urged to be vigilant for the presence of mink and to report any sightings to BBOWT via their web site. Read more about mink on the BBC web site.