Toxic, highly invasive pest plant found at Far North beach

RNZ News

4 days ago

Te Haumihi kaimahi Herbert Readon and Debbie Brown remove sea spurge from a newly-discovered site at Kapowairua/Spirits Bay.
Photo:
Supplied / Desmond Greer
A toxic, highly invasive pest plant that has already taken over large swathes of the Australian coast has been discovered at Kapowairua/Spirits Bay for the first time.
The find, at the remote and significant Far North beach, has set alarm bells ringing because it's at least 60km from the nearest known infestation at Te Oneroa-a-Tōhe/Ninety Mile Beach.
Northland Regional Council biosecurity manager Joanna Barr said the infestation was found by Ngāti Kuri's Te Haumihi team, whose members had been progressively surveying their rohe's coastline for the pest.
Barr said sea spurge (
Euphorbia paralias
) was native to Europe, but had likely arrived on currents from Australia, where it was a major weed on the southern coast.
The iwi's proactive surveillance work meant the invasive plant had been detected while still relatively small and in a contained area.
Te Haumihi programme manager Melanie Dalziel said the find included more than 50 plants in a six-square-metre area.
They included one large specimen, likely the original plant; 18 smaller but mature plants that had seeded; and 32 seedlings.
Dalziel said it was "very disheartening" to find the plants, but fortunate they had been located and removed before spreading further.
The team had now prioritised regular monitoring of beaches in the Ngāti Kuri rohe.
Barr said the surveillance work behind the latest find was part of a management programme delivered in partnership with iwi and hapū, the Ministry for Primary Industries, the Department of Conservation, and the Northland Regional Council.
The invasive sea spurge plant showing the flowers and seedlings.
Photo:
Supplied
During the past 12 months, 175km of Northland coastline had been surveyed, mainly on the west coast.
She said sea spurge had now been found in seven places around Northland: Poutō Peninsula, Waipoua River mouth, Mitimiti, Ahipara, Waipapakauri, Hukatere and now Kapowairua/Spirits Bay.
Plants in all those areas had been controlled, and the sites were checked every four months for new seedlings.
Barr said sea spurge was causing major environmental damage at many Australian beaches, displacing native plants and changing natural sand movements.
"It has the potential to overrun our native dune species and threaten the habitats of native birds," she said.
It also produced a milky, toxic sap that could cause skin irritation and temporary blindness in people and animals.
Barr said an adult plant could produce 5000 to 20,000 seeds per year, which travelled long distances on ocean currents.
"This means there's an ongoing risk of seeds making their way over and establishing along our long coastline, with the west coast being most at risk."
It was vital any sightings were reported, she said.
Sea spurge looked like a small shrub and typically grew to 50cm in height, though it sometimes reached one metre.
It had tightly packed leaves that were bluish-green in colour, with the stem often having a red tinge at the base.
Its flowers were yellowish-green, petal-less and in clusters.
Barr said anyone who thought they had found sea spurge should report it as soon as possible using the MPI hotline, 0800 80 99 66.
"Take some clear photos and please don't disturb the plants as the sap is toxic, and you could also spread the seeds via your clothing and equipment."
Finders should note the location as accurately as possible, ideally with GPS coordinates. Google Maps or the iNaturalist app could also be used to mark sites.
Barr said the invasive sea spurge looked similar to the rare native spurge, waiūatua/waiū-o-Kahukura (
Euphorbia glauca
), but the native spurge had much larger leaves that are 30-80mm long.
New Zealand linen flax (
Linum monogynum
) and the sand daphne/toroheke (
Pimelea villosa
) were also similar.
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