Alien killer ladybird puts 1,000 British species at risk

Published on Monday 29 June 2009 19:28

THE arrival of the invasive harlequin ladybird in the UK is likely to threaten more than 1,000 native species, scientists have warned.

The harlequin has become a common sight as it has spread across the country in the past few years – even invading houses in the autumn to hibernate over winter in warm spots.

The ladybird is originally from Asia, but it was introduced in Europe to control pest insects that were damaging crops and has since spread to the UK on fruit and flowers and by being blown across the Channel.

The ladybird has spread from Essex to Orkney in just four years, with London parks now recording staggering numbers of the insect.

The bug is a predator, which preys on a wide variety of insects, including the larvae of other ladybirds, caterpillars and even fruit, and out-competes with native species.

As a result, the species poses a major concern for UK wildlife, according to Dr Helen Roy, of the Centre for Ecology and Hydrology (CEH). Evidence from the US, which introduced the harlequin more than 20 years ago, shows "severe declines" in native species.

"We believe that the negative impacts of the harlequin on Britain will be far-reaching and disruptive, with the potential to affect over 1,000 of our native species," Dr Roy said.

"It's a big and voracious predator; it will eat lots of different insects, soft fruit and all kinds of things. Its reproductive capacity is also immense."

The harlequin ladybird has a variable appearance, is very difficult to tell apart from our native ladybirds and can chomp through more than 12,000 aphids a year.

But it is also known to eat such species as lacewing larvae, as well as pest insects carrying pathogens, depleting the supplies of the diseases that normally keep such species under control.

Scientists from five organisations are presenting information about the harlequin at the Royal Society Summer Exhibition this week, and warn that its arrival will mean "one winner, 1,000 losers".

The researchers are exploring how the few native enemies that exist, including fungal disease, male-killing bacteria, parasitic wasps and flies, could be used to control the population – or may evolve to tackle the harlequin naturally. One of the most promising ideas could involve encouraging a sexually transmitted mite which makes some ladybirds infertile.

Dr Remy Ware, of the University of Cambridge, who is working on how the mite could control harlequin populations, said it was a naturally occurring UK species which did not affect most British ladybirds because of their breeding cycles.

She said her team was examining if it could be artificially transferred to harlequins, where the ladybird's breeding pattern might allow it to be transmitted naturally, causing females to become sterile.

Dr Roy also said that if the harlequin were found in the habitat of rare ladybirds, such as the five spot which lives in just a few sites of disturbed river shingle in Wales, it might have to be physically removed to protect the native insect.

But she warned: "We haven't got a hope of blanket control of the harlequin ladybird. Anything we do here we'd have to do in other countries in Europe."