Field horsetail, a weedy fern, is spreading throughout wetter regions, competing with grasses, reducing the productive potential of land and impacting both grazing and cropping farmers.

Landcare Research, supported by the Rangitikei Horsetail Group, has been investigating potential biocontrol solutions to help control it and revealed last Friday a weevil (Grypus equiseti) has come out as the best candidate for the job.

“We are extremely pleased to hear they’ve found a weevil that, if approved, can help tackle the field horsetail issue affecting mainly the Rangitikei region. This will enable land to be returned to more productive use,” said MPI Acting Director Aquaculture, Growth and Innovation Alice Marfell-Jones. “Around $300,000 was invested over three years from the Sustainable Farming Fund which has gone towards understanding the effects of the field horsetail and investigate potential biocontrol options.”

Landcare Research researcher, Lindsay Smith, talked about the findings at a field day held in Bulls on Friday, 6 November. “Throughout our testing, we found the weevil to be one of the most damaging biocontrol agents causing significant damage to field horsetail. “The plant is attacked by both larvae and adult weevils, with the larvae burrowing down the weed’s stems and into its extensive root system.”

“Over the last three years, we have been testing the weevil in our biocontainment facility at Lincoln to confirm it is ‘host specific’ to horsetail and so will only damage horsetail and won’t pose a threat to other flora here in New Zealand. We will now be submitting an application to the Environmental Protection Authority to seek permission to release the weevil from containment. If we are successful, the weevil will be able to be introduced in to New Zealand to start work on field horsetail.”

“We are very grateful for the funding we have received over the last three years to be able to carry out this research. We couldn’t have done it without it.”

The Ministry's Sustainable Farming Fund invests in applied research and extension projects that tackle a shared problem or develop a new opportunity in the Primary Industries. Co-funders of the field horsetail research included Landcare Research, National Biocontrol Initiative, Rangitikei Horsetail Group, Horizons Regional Council, Rangitikei District Council, Rangitikei Aggregates and Wanganui District Council.