Scientists fight back against 'killer worm'

New Zealand breed is destroying local worms

By BBC NI rural affairs correspondent Martin Cassidy

Northern Ireland scientists believe a tiny gnat may be the answer to a giant sized problem posed by New Zealand flatworms which are devastating the local earthworm population.

The spread of the New Zealand flatworm is a serious issue for farmers, gardeners and fishermen who are already reporting shortages of earthworms for bait.

The loss of burrowing earthworms is now affecting soil quality with hard evidence emerging of compaction and poor drainage resulting from the loss of earthworms.

Dr Archie Murchie of the Department of Agriculture in Northern Ireland described it as a "horrible creature that feeds on its prey by wrapping itself boa constrictor-like around earthworms, digesting them externally and mopping up the resultant earthworm soup with its spongy mouth parts".

Archie Murchie: Plan will need a lot of thought

Little is known about the predators of flatworms in their native New Zealand.

But soil ecologists at Queen's University say a small Tasmanian gnat whose maggots are parasitic on flatworms could feasibly be introduced here to help the curb the spread of the "killer" worm.

Dr Murchie though said it was a move that would need a lot of thought.

"An awful lot more needs to be known about this gnat's biology, or else you could end up with a gnat problem as well as a flatworm one," he said.

The flatworm was first discovered in the province almost 40 years ago. It is thought it arrived here in potted plants.

Since then, the flatworm has been spreading beyond the Belfast area and its presence has now been confirmed in most parts of Northern Ireland.

Farmers transporting silage bales may inadvertently be helping the worm on its way.

The flat, liver-coloured creature can often be found sticking to the bottom of polythene silage stacks. Concerned about the depletion of local earthworm populations, the Applied Plant Science Division at Newforge Lane in Belfast is studying the flatworm's spread.

Flatworm is a worry for farmers and gardeners

There is already evidence that flatworm infestation is damaging soil structure by killing earthworms.

While local worms help break down organic matter and recycle plant nutrients within the soil, the New Zealand flatworm has no such work ethic.

The local earthworm more than earns its keep by burrowing which aerates plant roots and aids drainage but soil infested with flatworms shows signs of compaction and water-logging.

Such is the value of European earthworms that when introduced into New Zealand pastures, grass yields increased by up to 100%.