Hornwort control on Centennial Lake
14 March 2008
Control of the invasive weed hornwort (Ceratophyllum demersum) at Centennial Park Lake, Timaru is scheduled to take place on Tuesday 18 March 2008, weather and conditions permitting, MAF Biosecurity New Zealand said today.
Control work was undertaken after hornwort was identified in the lake and the north branch of the Otipua stream in February 2006. A survey of the lake in January 2008 showed hornwort was still present, although none was found at any site surveyed outside of the lake.
Control work will include the application of the aquatic herbicide endothal (Aquathol K/Aquathol Super K) by MAFBNZ contractors. Application will be by gun and hose or pellet spreader.
Previous treatments with the herbicide diquat weren't successful in eradicating hornwort from the lake. Reports from overseas suggest endothal to be effective in eradicating hornwort. Endothal was approved recently for controlled use in New Zealand.
"The lake will be monitored and a follow-up survey completed one month after treatment to assess effectiveness. The survey will include checking downstream of the lake at likely habitat sites," said Victoria Lamb, Senior Adviser - Pests and Pathways Team, MAF Biosecurity New Zealand.
"The restricted place notice put in place in February 2006, which closed the lake and affected stream areas to all use (including paddling, fishing, kayaking and swimming), will remain in force until the hornwort has been completely eradicated.
"Additional signage was erected this summer to ensure that members of the public were aware of the ongoing restrictions on access to the lake. We are asking the public to help contain hornwort by ensuring they do not enter the lake until control operations are completed," said Victoria Lamb.
Hornwort is an invasive weed established in the North Island. It is not yet thought to be established in the South Island. It grows rapidly, forming dense mats that choke waterways and is difficult to eradicate.
Hornwort is a free-floating plant with no roots. It has long, dark green stems with forked leaves arranged in whorls of 7-12. Hornwort may be found in waterways and garden ponds. Members of the public are asked to keep a look out. Any sightings should be reported to MAF Biosecurity New Zealand on 0800 80 99 66. For more information about hornwort go to www.biosecurity.govt.nz/pests/hornwort.
- For further information contact Judith Hamblyn, Senior Communications Adviser on 04 894 0687 or 029 894 0687.