Skip to main content
Published: 2012-07-31 00:00:00

Waikato Regional Council has been playing a central role in moves designed to make spraying of aquatic weeds more cost effective and to get formal approval for such spraying.

The Environmental Protection Authority (EPA) has announced today it is seeking submissions on an application to allow a number of herbicides to be used over water to control aquatic pest plants. The herbicides have been used for many years over water already but the application is designed to secure the necessary formal approval under the Hazardous Substances and New Organisms (HSNO) Act.

The application is being made by the Agricultural Reassessment Group (ARG), on behalf of 12 regional councils, including Waikato, as well as the Department of Conservation, Ministry for Primary Industries, Land Information New Zealand and Mighty River Power.

The group is seeking approval to use herbicides containing one of four active ingredients (haloxyfop-R-methyl, imazapyr isopropylamine, metsulfuron-methyl or triclopyr triethylamine).

These substances are currently approved for use on land in New Zealand. They target a range of New Zealand’s worst weeds, including Manchurian wild rice, Spartina, alligator weed, yellow flag iris and some grasses and sedges. But they are not formally approved by the EPA for use over water, even though many councils and agencies have been using them to control weeds that can grow in or near water.

This gap in approval for use of the herbicides to control aquatic weeds was discovered by Waikato Regional Council’s biosecurity and heritage group last December when, in the interests of efficiency and saving money, it was looking to streamline the consenting process for applying herbicides to aquatic weeds.

“As we looked at streamlining our aquatic weed spraying consent process we saw that, while such spraying over water was allowed under the Resource Management Act, we needed approval to do it under HSNO,” said programme manager Kevin Collins.

“We immediately ceased any spraying of aquatic weeds with the herbicides and approached the EPA about what we needed to do to become compliant with HSNO. The combined application from ARG to the EPA was the end result.”

Mr Collins said Waikato would work closely with the EPA and the other parties to the application. “We want to make sure we have all the necessary approvals before resuming general spraying of aquatic weeds with the herbicides.”

In its application, the ARG states that the use of the herbicides over water will complement existing pest plant control methods and help fulfill the group’s statutory obligations under the Biosecurity Act to control and eradicate, where possible, invasive pest plant species.

The ARG has evaluated the potential risks to organisms within the aquatic environment from uncontrolled use of the substances on to or into water. It considers that these risks can be reduced by a number of proposed controls on the use of the substances. The ARG’s application was submitted to the EPA last month. The EPA has indicated a decision is likely on the application before the end of September 2012.

Meanwhile, Waikato Regional Council is urgently seeking special, emergency permission from the Government and the EPA to use one of the herbicides to spray a small infestation of alligator weed at the Ruahorehore Stream near Waihi. “It’s a catch-22. Under our existing resource consent we must spray before September but the EPA decision on the ARG application won’t be issued before then. Alligator weed is a particularly aggressive pest plant and spraying is the most effective way to help stop it spreading when it is growing in an aquatic environment,” said Mr Collins.