New weeds threaten South

Merging aquatic weeds are a new threat to the south of the South Island with the potential to cause multimillion-dollar damage, the New Zealand Biosecurity Institute's annual conference at Queenstown was told yesterday.

Niwa scientist Paul Champion said he wanted to "scare" South Islanders with his speech on new threats to the deep South in the next 30 years.

Mr Champion said lagarosiphon and didymo were the "big nasties" but newer species were emerging as a threat.

Parrot feather, hornwort, egeria, senegal tea and alligator weed were starting to rear their ugly heads in South Island waterways.

Both clasped pondweed and bogbean had been found at Queenstown, he said.

He said power companies should be "very afraid" as aquatic weeds had the power to smother hydro lakes and disrupt generation of millions of dollars worth of electricity.

Rowan Wells, of Niwa, offered an "exciting" solution for aquatic weed eradication.

He said trials of endothall, a herbicide, produced "incredibly good results".

It was ideal for killing noxious weeds.

Endothall was non-toxic, biodegradable and was no threat to human health.

It could target the roots of aquatic weeds and leave native plants alone.

More than 200 delegates are attending the three-day conference at Queenstown this week.

joanne.carroll@odt.co.nz