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Another hurdle for 'poison-free Christchurch'

Antoinette Spicer

A weed-killing technology trial funded by the Christchurch City Council has ended early due to it being ineffective.

In February last year, the Avon-Ōtākaro Network revealed it would start a 12-month trial to test a ‘revolutionary’ electrothermal control tool, which kills weeds by sending 5000 volts down root systems.

The trial was a key part of the council's initiative to switch out poisons for green sprays.

Avon-Ōtākaro spokesperson Evan Smith described the technology as a ‘once in a lifetime opportunity’ and said it was the only one of its kind in the southern hemisphere.

Spokesperson Sarah Butterfield said she hoped to see half a dozen electrothermal control tools used in Christchurch.

However, Avon-Ōtākaro spokesperson Kyle Sutherland confirmed last week the network ended the trial early at the end of 2019. He said the machine was less effective than hand weeding.

The council was applauded three years ago when it drastically cut its reliance on glyphosate, commonly sold as the weedkiller Roundup, after it was classified in 2015 as being "probably carcinogenic to humans" by the International Agency for Research.

It agreed in 2016 Roundup should only be used on sites closed to the public or in places where no other method is practical.

However, councillors were told in February last year the money budgeted for the alternatives was insufficient – and that contractors were struggling to maintain weeds in parks without using Roundup.

A 1 NEWS investigation last year revealed the council and its contractors still use glyphosate, the active ingredient in products like Roundup, on 2.6 million metres of local pavements.

A request under the Local Government Official Information and Meetings Act showed the council dramatically reduced its glyphosate use in public parks after the vote, using a new organic plant-derived herbicide in its place across 1,570,400 square metres of amenity gardens.

However, as they can’t use that organic weed killer near drains, they have struggled to cut back use in the same way on the streets.

Documents show the council has introduced a chemical-free steam treatment to 19 per cent of footpaths, but continues to spray glyphosate on the other 81 per cent. In total, that means the chemical is still sprayed on as much as 2,615,454 metres of footpaths in Christchurch.

Information requested under the Official Information Act revealed the Christchurch City Council spent $600,000 last financial year on roadside spraying across the city, and an additional $41,706 on the Banks Peninsula. The council said that figure included spraying and other duties carried out at the same time of servicing.

A council spokesperson said the control budget for spraying citywide was only $350,000 so far this year.

"We will always look to reduce costs wherever possible," he said.

While the electrothermal control tool trial was a failure, he said the council was looking to fund other weed-killing technologies or green alternatives in the future.

"An example of this is a steam/thermal weed control, which was trialled and implemented into the transport road landscape contract on April 2018, and is still used.''