Work's begun to clear a problematic plant clogging the water of a major tourist destination

Land Information New Zealand's leading the charge at Otago's Lake Wanaka, where divers are attempting to eradicate lagarosiphon .

The two-month long process will see four rugby fields worth of hessian mats laid on the Lake's floor, to smother the weed.

Biosecurity Manager, Tracey Burton says divers will be building on progress made over the last two decades.

She says the work is essential, as the plant can take over and choke waterways, smother native plants and impact the lake's use -- if left untouched.