Photo: Weedbusters
Land Information New Zealand admit there's a risk the invasive hornwort weed could spread from Lake Karāpiro to the South Island with the Maadi cup starting next month.
Spray will begin next week at the lake ahead of the secondary schools rowing regatta at the end of next month, where thousands of students from hundreds of schools are set to compete.
With Maadi cup on-the-way, there is the potential for the weed to travel back to every waterway in the country.
Land Information NZ Biosecurity manager Tracey Burton told Morning Report that was it was a risk that had been in the lake for many years.
"This Maadi Cup and other events in Lake Karāpiro have been occuring for a longtime and we believe we've got some got measures down at that boat ramp, down where people are taking their gear out of the lake, but we do need everybody to be onboard.
"This isn't a problem that any one organisation can fix itself, this weed is spread by people, and it just takes a piece of weed the size of my finger nail to be spread into a new lake, to be able to start a new infestation."
The weed is not in the South Island or the neighbouring Rotorua lakes.
Burton admitted the Maadi cup was a huge risk and had "every finger crossed" the event would have minimal weed impacts.
The 2024 Maadi cup. Photo: © Picture Show Ltd 2024
A boat and a helicopter will be used to spray weed near boat ramps, ski lanes and popular swimming spots next week.
When asked why the spraying wasn't done earlier, she said they were limited by their contractors, weather and the school holidays.
"We are limited by the tools we can use, and the people that can apply this spray and unfortuanly that wasn't able to happen before Christmas."
Burton said hornwort was New Zealand's worst submerged weed and it's growing in Lake Karāpiro.
"This is a non-native weed that has come into New Zeakland, and it's able to grow faster, taller and more densely than any of our native plants."
She in the Waikato they were dealing with weed beds over eight metres tall - taller than a house - and they didn't have any "true roots".
"They are forming these really large dense surface reaching weed beds that can dislodge and float down the river system.
"We've got limited tools in our tool box to be able to control this weed - once it's in a lake system, we can't get it out."
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