A fresh, determined effort to prevent didymo - commonly known as rock snot - from entering Wairarapa waterways is being made this summer.
Greater Wellington Regional Council will have dedicated staff out and about in Wairarapa telling people how they can avoid introducing the thick, algal slime from invading rivers and streams, along with tips on keeping out other unwanted aquatic weeds.
The council's pest plant team leader, Richard Grimmett, said anyone casting a fly or boating on a river over summer was likely to encounter a council officer who would be offering advice about the threat of didymo.
Didymo is rampant in the South Island but hasn't yet been discovered in North Island waterways. It impacts on the health of the river or stream by forming a thick layer of slime over rocks.
Mr Grimmett said the means of keeping Wairarapa, and other North Island waterways, free of didymo was "pretty simple".
"It's all about checking, cleaning and drying your gear between trips to the river.
"Check all your gear for traces of algae or aquatic weeds. Gear can be a boat, boat trailer, boots, fishing gear, nets or anything else that you take into the water.
"Check it, clean it and dry it before you enter another waterway."
Mr Grimmett said this summer was the fifth in a row the council has been spreading the message.
People were very receptive to being told, as nobody wanted to see waterways choked with algae or weeds, he said.