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Council to consult community after weed control trial

August 14, 2003

North Shore City Council will consult the community on various options for controlling weeds on roads and footpaths.

The council's works and environment committee this week reviewed the results of trials on several weed control methods and decided to seek public views on the available options, focussing on health, effectiveness and costs. It will then review its policy taking into account residents' concerns about the use of herbicides.

In 1993 the council introduced hot water as a method to control weeds on footpaths and road edges, following concerns from some residents about the use of chemical sprays.

Chairperson of North Shore City's works and environment committee, Joel Cayford, says the trials have shown that hot water has proved to be expensive, and only temporarily effective, with growth bouncing back from well-established weeds growing through paving gaps, especially during summer.

"We conducted an extensive nine-week trial, beginning in May, and tested hot water, mechanical cutting, and three different herbicides. The herbicides tested included Organic Interceptor (a pine oil-based product); Biosafe (a coconut oil-based product); and glyphosate 360, (similar to Round-up)," Councillor Cayford says.

Each method was tested over the same early winter period, with special note being taken of how quickly leaves turned brown, whether the weeds regrew, and by how much. Results were photographed and recorded.

Hot water and mechanical methods achieved the quickest result, but regrowth was evident after two weeks. While chemical methods took a couple of weeks to completely kill the visible growth, only glyphosate was effective long-term.

For all methods except the glyphosate 360, weed regrowth after application reached at least 30 centimetres after 59 days. There was no regrowth after using glyphosate 360.

The trial also found that depending on the application rate, the product based on pine tree oil was up to four times more expensive than glyphosate 360.

Joel Cayford says the council will now look at funding options for a public information and consultation programme. This will include information about the effectiveness, frequency, costs and health risks of options.

" We've not made this decision to consult on weed management methods lightly and I'm aware of how controversial the issue of chemical sprays is for many North Shore residents. However, we need to test new methods and closely involve the community in any possible policy change in such a significant area of council activity," Councillor Cayford says.

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