A large digger isn’t something usually seen in a protected wetland, but it’s proven vital in a collaborative effort to remove an invasive weed species.

The invasive plant Cuscuta campestris – also known as “golden dodder”, and more commonly referred to as simply “cuscuta” – was previously only known to be in north Waikato.

That was until it was identified near the Piako River in 2024, on a stretch of the Kopuatai peat dome in DoC’s Hauraki operations district.

Cuscuta is a parasitic plant that sucks nutrients from other plants and has the potential to smother native plant species.

It can grow on a wide variety of plants, including pasture crops and waterfowl food, compromising both recreational and biodiversity values wherever it is found.

In a statement released this week, Biodiversity ranger Rachel Langman said cuscuta was discovered by DoC staff at Kopuatai while doing routine trap checks.

They called on colleagues from DoC’s Waikato district for initial support in how to address the infestation.

“Kopuatai is a Ramsar site and an important habitat for threatened native species like matuku-hūrepo/bittern, mātātā/fern birds, and native fish.

“Cuscuta presents a real threat to those species if left unchecked. New Zealand’s native species are unique and special, and most are only found here. Once they’re gone, they’re gone forever.”

To address the Kopuatai infestation, staff from DoC and Waikato Regional Council collaborated on a plan, which saw a large digger rolled out on to the site in January.

The digger’s role was to remove the top 10cm of soil – containing cuscuta seed - and bury that soil in a 1m deep hole so the seeds couldn’t germinate.

This will prevent the weed from growing or being spread to other areas through human activity.

“Although the digger method seems drastic, it was identified as the best approach to controlling the infestation before it became unmanageable.

“We expect grasses, which are not a host of cuscuta, to regenerate where the topsoil has been removed.

“Our team will continue to monitor the area regularly to prevent the reinfestation of this plant pest.”

If anyone sees cuscuta on land managed by DoC, they should call 0800 DOC HOT and, if possible, provide the exact location so rangers can investigate.

New Zealand has more threatened species than anywhere else in the world, with over 4000 species considered threatened or at risk of extinction.

Find out more about DoC’s work, and how you can help, on the DoC website.