The Environmental Protection Authority (EPA) wants people’s views on an application to release four different insects to control the spread of purple loosestrife, an invasive wetland weed.

Horizons Regional Council has applied to introduce the four insects in the Manawatū-Whanganui region as biocontrol agents to target different parts of the purple loosestrife plant, Lythrum salicaria.

The insects are two beetles that eat the plant’s leaves ( Neogalerucella calmariensis and Neogalerucella pusilla), a root-feeding weevil ( Hylobius transversovittatus), and a weevil that eats purple loosestrife flowers ( Nanophyes marmoratus).

Purple loosestrife is a bushy plant that forms high, impenetrable stands which overwhelm other plants, threatening native biodiversity and significantly impacting wetland ecosystems.

It is native to Europe, parts of Asia, and Australia, and was introduced to New Zealand as an ornamental herb before naturalising in the wild in the 1950s.

The plant can be found in Canterbury, the West Coast, Wellington, and Manawatū-Whanganui regions, with the largest populations at Lake Horowhenua and in the surrounding area.

Purple loosestrife is considered a noxious weed in the United States of America and Canada, where it has affected large areas of wetland ecosystems.

The two leaf-eating beetles proposed to control this weed are from Europe and Asia, while the two weevils that feed on the roots and flowers are from Eastern Europe.

"The applicant’s risk assessment includes studies that show they are highly unlikely to harm native plants or animals," says Dr Chris Hill, General Manager of Hazardous Substances and New Organisms.

"None of these insects bite or sting, so there is no potential risk to people."

Horizons Regional Council says the same insects have been used together as biocontrol agents in the USA, where they reduced purple loosestrife infestations by up to 90 percent in some areas within the first 10 years.

The public consultation enables the wider public and people in relevant industries to provide additional information on the risks and benefits of introducing four new insects as biological controls for purple loosestrife.

Submitters can provide information, make comments, and raise issues to contribute to the EPA decision-making process.

Submissions close at 5.00pm on 17 October 2023.

Read more about this application

© Scoop Media