Rotting weed causing stink in Rotorua

A putrid smell is getting up the noses of some Rotorua residents - and it's not sulphur.

Okawa Bay residents say it's the worst it's been in decades, but the regional council can't do anything about hectares of hornwort growing in Lake Rotoiti - just yet.

After two big storms in the last month tonnes of hornwort has been blown into the bay and is breaking down to smell like rotting vegetables.

The problem is particularly bad at the southern end of the lake where the weed has been blown by strong winds leaving it to pile up about 20m into the lake.

Long time Okawa Bay resident Robin Sinclair said the bay was very good at growing hornwort, estimating an area of 42ha was covered by it before it was blown onshore.

"It's never been this high before," he said.

Mr Sinclair said he would like the Bay of Plenty Regional Council to either spray the bay with Endothall (a pesticide which can be used as an aquatic herbicide) or bring in its new lake weed harvesting machine to clear the bay.

"Apart from the smell, it's not a good look for a tourist town.

"They are using the weed harvester on Lake Rotoehu where there is virtually no population. It would be put to much better use here.

"They [regional council] use a lot of interesting terminology when telling you they are not going to do anything about it," he said.

Bay of Plenty Regional Council lakes operations manager Andy Bruere said he was well aware of the problem and sympathised with Okawa Bay residents.

He said a lake weed harvesting machine had been purchased by the regional council and once operational would be used to clear Lake Rotoehu first.

Mr Bruere said in the past they had hired a harvester from Mighty River Power, but that was no longer available.

He said a proposal by a company that was going to buy a harvester and clear the lakes under contact to the regional council had fallen over at the last minute so they had bought their own machine.

"It only arrived last week and needs to be trialled and licensed to be used on lakes.

"With all due respect, the problem is quite a bit bigger on Rotoehu, about 80ha of weed needs to be cleared from that lake to prevent further algal blooms.

"Okawa Bay is small, but it is busy and very important to us as well."

Mr Bruere said water clarity on Lake Rotoiti had improved greatly which had caused more weed growth.

"But this won't happen every year."

Amora Lake Resort general manager Vivek Singh said the problem had affected the business, but was more of an issue for time share clients than those who stayed a short time.


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