North Canterbury Transport Infrastructure Recovery (NCTIR) teamed up with Kaikōura Land Management and Biodiversity Advisor, Heath Melville, to celebrate conservation week, holding a biosecurity day at one of Kaikōura’s most impressive wetlands.

Hapuku Scarp Wetland was the focus for the latest round of conservation-action, with many hands making light work at NCTIR’s community day on 19 August.

Tradescantia fluminensis the target of weed control

Thirteen NCTIR staff donned gloves and boots to tackle the invasive weed species Tradescantia fluminensis, otherwise known as ‘wandering willie’.

This weed grows in large, dense mats across the ground, which prevents native species from regenerating, and smothers native groundcovers, ferns and seedlings.

“It was awesome to involve NCTIR in the initiation of this new stage of weed control, at a site we are so very fond of,” Melville said.

“It has huge significance as far as wetlands go and there’s definitely a few weed busters in the making at NCTIR, which is good to see.” 

Hapuku Scarp Wetland gets a tidy-up

Hapuku Scarp Wetland is one of Canterbury’s best examples of a coastal bush scarp wetland, and hosts some of New Zealand’s southernmost tawa and black maire trees.

The joint effort saw a large area of weeds cleared, with a local contractor heading in to spray any regrowth over the coming months.

Further work is required, as even the smallest fragment of stem or leaf can regrow into a dense mat.

“It was extremely satisfying to see what was a carpet of green turn into brown earth, with ferns, kawakawa and an array of native seedlings peeking through,” said NCTIR Communications Coordinator, Naomi Ambrose.

Weed control assists biocontrol work

The weed control effort during conservation week sits alongside the QEII National Trust’s recent work, having released several biocontrol agents into the site to control the spread of the Tradescantia. 

Biocontrol agents are insects that utilise the weed as a food source and according to Melville, “there has been great success in the control of the species the North Island, but it’s been slow to make much difference here in the south.” 

Biocontrol can assist in containing large infestations of pest weeds like Tradescantia, gorse, and broom.

The Canterbury Regional Pest Management Plan provides the regulatory requirements for priority pests (including pest plants) across the region, while being a key component for our wider biosecurity programme.

Step-by-step action to contain Tradescantia

Since the site was fenced off and registered as a QEII covenant, the weed has rendered much of the underlying layer of vegetation into a single species area, with the diversity being lost.

Following the work by QEII National Trust, it was decided to try to contain the spread of Tradescantia using intensive hand-weeding where native flora is still present in the lowest vegetation layer.

“It will be followed up with careful use of herbicide around the native flora present to eventually create a buffer zone around the major infestation of the weed, which will require yearly herbicide application,” Melville said.

“There’s so much value in targeted weed control in ecologically-rich areas such Hapuku Scarp Wetland, and it’s nice to have a reason to take people to such sites and experience them for themselves.

“The more we can embrace biosecurity for the protection of our biodiversity, the better chance we have at halting the decline of our native species.”

More information

Look out for other wetland work in Kaikōura by keeping an eye on our latest news.

Local landowners and managers who are interested in assistance or resources for protecting or enhancing wetlands on their property can get in touch with our Kaikōura office by calling 03 319 5781.

• Managing pest plants
• Canterbury Regional Pest Management Plan

 Images credit: Heath Melville