An invasive South American weed which authorities are trying to remove from Lake Taupo is already established in a number of Rotorua lakes.
Egeria densa was recently discovered growing in the Taupo boat harbour prompting a survey to discover how far the weed has spread.
Although authorities were concerned at finding the
weed in Taupo it had been established in Rotorua's lakes for some time, Environment BOP environmental scientist John Gibbons-Davies said.
Lake Rotorua, Okataina and Tarawera were among the lakes where the weed had been found, Mr Gibbons-Davies said.
However, because it was so well established it was no longer regarded as a serious threat.
"Once the weeds get into the lakes they're very hard to eradicate, he said.
Because only isolated patches were believed to be growing in Taupo it could be easier to eradicate the weed before it established itself, he said.
While 10 years ago there was more than 400 hectares of the weed in Lake Rotorua a large storm had cleared much of it, Niwa aquatic scientist Rohan Wells
said.
Eradicating the weed from Rotorua's lakes would be "impossible" Mr Wells said.
Egeria densa had not had any major negative effects on trout or other lake plants in the area.
The weed beds even provided a good nesting ground for insects which were a food source for trout, he said.
The weed was often spread after it became entangled in boats and trailers.
- DAILY POST (ROTORUA)
