Science - December 6, 2007

Beware of the harlequin ladybird

The multi-coloured harlequin ladybird (Harmonia axyridis) should never have been released as a biological pest control agent in north-western Europe, writes entomologist Professor Joop van Lenteren and a number of colleagues in an online pre-publication edition of the journal BioControl.

The harlequin ladybird looks attractive, but is rapidly becoming a worldwide pest.
The ladybird, which varies in colour from red to black and has differing numbers of spots or patches, was introduced for aphid control in Europe in 1995 by the Belgian firm Biobest. On the instructions leaflet the bug is described as an ‘aphid guzzler’ that is suitable for release in greenhouse crops as well as open field crops, parks and public spaces. It was not long, however, before reports started coming in that the ladybird was doing well in the wild and was happily eating the larvae of indigenous fellow-species members. The harlequin ladybird has also damaged the reputation of this otherwise popular species by occasionally biting humans. In North America the ladybird even seems to be turning into a pest itself in fruit.

In the lead article in the coming issue of BioControl, which is almost entirely devoted to H. axyridis, Van Lenteren, Dr Antoon Loomans of the Plant Protection Service of the Netherlands and two Swiss colleagues analyse the dangers of the ladybird. They do so by means of a recently developed method of risk evaluation for natural enemies. The researchers conclude that harlequin ladybird should never have been permitted for use as a natural enemy for a number of reasons. One is that it preys on too many different kinds of animals and another is that it can travel over fifty kilometres a year. The scientific literature available on the species in 1995 was also ‘sufficient to reject import and release of this species’. According to the authors, the matter underlines the ‘urgent need for harmonized, world-wide regulation of biological control agents’.

Elsewhere in the journal, Dr Theodoor Heijerman of the Biosystematics group and three colleagues from the Plant Protection Service make predictions based on the Climex distribution programme: H. axyridis looks set to stay in Mediterranean Europe, South America, Africa, Australia and New Zealand.

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