11 Nov 2015

British Weevil chosen to fight invasive weed

2:35 pm on 11 November 2015

The days of Field Horsetail, an invasive weed, could be numbered, with the selection of the British Weevil as a biocontrol agent.

Field Horsetail

Field Horsetail Photo: 123rf.com

If given the green-light by the Environmental Protection Authority, the weevil could start its work next year.

Field Horsetail is widespread in parts of the North Island, the upper South Island and on the West Coast.

Landcare Research has been trialling a number of biocontrols in laboratory conditions and was certain the British Weevil, Grypus equiseti, was host-specific to horsetail and would not pose a threat to other plants.

Researcher Lindsay Smith said they tested four different Northern Hemisphere control agents and settled on the British Weevil

"The Weevil comes out on top for the fact that both life stages, the adult and lavae feed on the plant and in particular the larvae burrows down into the roots and we feel can do significant damage to the plant."

He said the weevil will not eradicate the plant but would reduce it.

"Rather than being a dominant plant on the landscape it will become just another plant in the landscape."

He said researchers were confident it was host-specific to horsetail.

"In our containment facility here at Lincoln we have run through a range of tests where we expose the plant eating stages of the weevil to various other plants...and we score the damage, we assess how many eggs were laid on other plants and the Horse tail weevil comes out as being exceptionally clean. It feeds on no other plant."