November 23 2012

Lagarosiphon – a weed wrecking boating and swimming spots

Lagarosiphon is a major threat to some of Otago’s best holiday lakeside spots. With summer holidays around the corner it’s time for boaties to do their bit to control this pest plant.

Boaties, and everyone using lakes and rivers, can help halt lagarosiphon’s spread by ensuring they Check, Clean and Dry their craft and equipment of accumulated weed.

In the worst-affected areas, where they are most likely to see the weed: Lakes Wanaka, Dunstan, Roxburgh; and the Clutha River/Mata-Au; it is particularly important to stop its spread.

The dispersal of fragments of lagarosiphon into a river or lake can lead to new infestations that can spread quickly. Boaties and other people using recreational equipment that can pick up the weed should destroy it as soon as they find it on their equipment.

Otago Regional Council (ORC) director regional services Jeff Donaldson says the council monitors high risk areas for the spread of lagarosiphon.

Didymo is another troublemaking algae which can cause problems in waterways at this time of the year, including forming massive blooms in streams, rivers, and lakes.

Mr Donaldson says this pest can be spread by a single drop of water.

“Even if you can't see it, you could be spreading it.”

As with lagarosiphon, the best way to contain didymo is to Check, Clean, and Dry.

This involves:

Check –- remove all visible threads or clumps of weed and algae from gear and clothing

Clean –- soak or scrub all items of equipment for at least one minute with a five percent measure of biodegradable dishwashing solution – or one tablespoon of detergent per 250ml

Dry –- after cleaning equipment, or if cleaning is not practical (e.g. animals), dry to touch then leave for a further 48 hours before entering another waterway.

“We are asking boaties moving between waterways to Check, Clean, Dry all equipment that has come into contact with river or lake water – particularly boots and anchor wells,” Mr Donaldson said.

Water absorbent materials such as boots need to be soaked for a few minutes to allow thorough saturation.

Mr Donaldson said following these simple procedures would help slow the spread of all freshwater pests like didymo and lagarosiphon throughout South Island waterways.
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