Weed discovery puts boaties on alert
14 May 2012
An invasive aquatic weed has been found in Lake Rotorangi, prompting a request for recreational users of the lake to
help prevent it spreading.
Hornwort, also known as coontail, is highly invasive. Picture courtesy of NIWA
Boats and other equipment should be well cleaned before departing Lake Rotorangi to help prevent the spread of hornwort,
also known as coontail.
Hornwort is classed as an unwanted organism under the Biosecurity Act, and its sale, propagation and distribution is
banned. It rapidly invades most freshwater habitats, crowding out native species and impeding drainage, irrigation and
other uses.
“Hornwort is not listed in Taranaki’s regional pest plant strategy but it is banned nationally,” says the Taranaki
Regional Council’s Compliance Manager, Bruce Pope.
“We’re particularly concerned about this discovery because many boaties who use Lake Rotorangi also use nearby Lake
Rotokare, where the local community has put a great deal of effort into establishing a pest-free sanctuary.
“We’d also like people to watch out for it in other Taranaki waterways, and let us know if they see it.”
Hornwort is a submerged freshwater weed found in still and flowing waters, growing in depths of up to 16m in clear, deep
lakes. Leaves are finely divided, with minute teeth which make the plant feel rough to the touch. It lacks roots but has
modified leaves that anchor the plant in bottom sediments.
It is widely distributed in the North Island but until now there have been no confirmed reports of established
infestations in Taranaki.
Mr Pope says its discovery here is a reminder that boaties and other recreational users should check and remove all
weeds and unwanted material from boats and equipment before leaving any waterway.
ends