MEDIA RELEASE

Aquatic weed highlights risk to lakes

For immediate release: Monday 22 August 2005

A flourishing infestation in Lake Rotoehu of one of the worst types of aquatic weed has highlighted the risk that boats can pose to the Rotorua lakes.

Hornwort (Ceratophyllum demersum) has spread rapidly in Lake Rotoehu over the past year, forming a thick mat covering several hectares. Environment Bay of Plenty pest plant coordinator John Mather says it was probably introduced by a boat coming from Lake Rotorua, Lake Rotoiti or Lake Tarawera, which have hosted hornwort for a number of years.

Mr Mather is now concerned boaties might inadvertently transfer hornwort from Lake Rotoehu into nearby Lake Rotoma, which does not have it. He reminds all boaties to be extremely careful to check their boats for weeds when leaving the lake and before entering a new lake.

Hornwort has free-floating stems that can grow up to 10m long. “So it can easily get tangled in a boat’s propeller or trailer. It only takes one small piece to start a whole new infestation somewhere else.”

Staff recently helped Land Information New Zealand contractors survey the infestation and control key areas with herbicide. The work targeted hornwort around the main boat ramp, to reduce the risk of the weed getting picked up by boats leaving the lake.

With its long, free-floating stems, hornwort can easily get tangled in a boat’s propeller or trailer – and end up causing problems in a new lake.

ENDS

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