INVASIVE HALEQUIN SPECIES FORCES THE LADYBIRD OUT

Photo courtesy of anemoneprojects

Scientist’s findings have recently shown that a rapid decline in Ladybirds native to the UK and other European countries is being caused by the invasive harlequin species as it spreads.

The invasive Asian species of harlequin was originally brought into Europe to act as a commercial pest control for crops and has subsequently become a pest itself. Arriving in 2004, the harlequin has led to the decline of seven out of eight UK ladybird species over the five years following its arrival. The study, conducted by the Centre for Ecology and Hydrology (CEH), showed numbers of the two-spotted ladybird (Adalia bipunctata) to have fallen by close to half (44%), a species that had once been common in the UK. Scientists have said that some species are “near the threshold of detection” and are giving warnings of potential damage to ecosystems’ “resilience”.

Helen Roy from CEH in Wallingford, Oxfordshire, said “this study provides strong evidence of a link between the arrival of the harlequin and declines in other species of ladybird”, “it’s a very real decline, which should be put amongst a whole other set of factors putting ladybirds in a more fragile situation”, she added.

The invasive harlequin species shares the same habitat as the two-spotted ladybird, both residing on deciduous trees, however because of the two-spotted ladybird’s inferior size, the harlequin out-competes it for food and also feeds on its larvae. It would appear that their co-existence within the same habitat has a pivotal effect on the native species’ decline as the only UK species to appear unaffected by the harlequin is the seven-spotted ladybird (Coccinella septempunctata), which is a similar size and has a different habitat subsequently causing no direct competition for the same niche.

Tim Adriaens, from the Research Institute for Nature and Forest (INBO) in Belgium said, “Ladybirds provide an incredibly useful ecological function by keeping aphids in check” and "at the continental scale, the arrival of the harlequin could impact on the resilience of ecosystems and severely diminish the vital services that ladybirds deliver”.

Unfortunately there is currently no effective and selective way of eliminating the harlequin population and due to the huge similarities in their morphology to native species, gardeners are being advised to be extremely cautious if they are attempting to control the pests themselves.

By Lucas Lowe