Over The Horizon

Wild Kiwi Worms Ravage Britain

New Zealand plant exports to Britain and Europe are under threat from a worm found in most local gardens. The New Zealand flatworm is wanted, dead or alive, in Britain, where it is feeding on valuable earthworms, with serious financial and ecological implications for agricultural land and wildlife. The flatworm is posing such a threat to British agriculture that it has been scheduled under the UK Countryside and Wildlife Act, making it an offence to spread it knowingly.

Landcare Research zoologist Dr Gregor Yeates says the New Zealand flatworm -- which looks like a flat rubber band -- is very common in New Zealand soils and more than 50 native and eight introduced species have been found in this country; Britain has only eight. He has found more species in his own garden than in the whole of Britain.

In Britain, the New Zealand flatworm feeds on valuable earthworms. After first anaesthetising its prey, the worm secretes enzymes which digest it externally and then sucks in the resulting "soup". Little is known about the biology of the flatworm, but in general they appear to be successful predators on other animals such as slaters, snails, slugs and insect larvae.

The possible quarantining of New Zealand plant exports is a real threat, but nurseries here can make an easy transition to flatworm-free conditions with good management techniques.

The flatworm was first noted in Northern Ireland in 1963 and is now widespread through Ireland and Scotland. In Scotland it has eradicated earthworms, or reduced numbers to below detectable levels, in some areas. Because it feeds on topsoil-mixing earthworms, it is seen as a threat to earthworm populations as well as soil structure and farm productivity. While the main concern is for agricultural land, many records are coming from garden centres, botanical and home gardens.

Long term, the eradication of earthworms has serious implications because of their important role in nutrient cycling, maintaining soil structure and drainage. There could be flow-on effects to wildlife which feed on earthworms, such as badgers, moles, shrews, foxes and birds.

The flatworm has no natural enemies and no chemicals have been approved for its eradication.