Lake reopens after invasive weed disappears

CENTENNIAL Park Lake has been reopened after a survey revealed no sign of the highly invasive freshwater weed hornwort.

MAF Biosecurity New Zealand closed the lake and the north branch of the Otipua Stream to all use (including paddling, fishing, kayaking and swimming) in February 2006 after hornwort was discovered.

Last March, the aquatic herbicide Endothal was used in the lake to combat the weed.

Hornwort is widely established in the North Island but has been found at only two sites in the South Island near Motueka and in Centennial Park Lake.

Annual surveys of the lake and stream will continue for five years, and if no hornwort is found it will be declared eradicated from the site.

Hornwort is a free-floating plant with no roots. It has long, dark green stems with forked leaves arranged in whorls of seven to 12. Its stems are easily broken and can contaminate boats, fishing and recreational equipment.

It can survive for months in wet spots such as under the floor or in the anchor well of boats.

- © Fairfax NZ News