Council to trial weevils to control weed in lake at Ocean Shores

Published on 25 September 2018

Byron Shire Council and Rous County Council will this week be releasing thousands of weevils in the lake at Waterlily Park at Ocean Shores as a way of controlling the invasive water weed Salvinia molesta.

Earlier this year the Salvinia weed had completely covered the lake and in July Council used mechanical harvesters to remove as much of the weed as possible.

Council’s Open Spaces Coordinator, Malcolm Robertson, said removing the weed was the first stage and now the focus is on controlling it so that it does not take over the lake again.

“Salvinia molesta is an extremely difficult plant to control because it has a very fast growth rate and can double in mass every couple of days,” Mr Robertson said.

“Plants can also grow from a very small fragment so control has to be a multi-pronged approach and this is why we have decided to use a biological control agent, the weevils, to see if they will be able to keep the growth and spread of the Salvinia to manageable levels,” he said.

“There are really only two options for the ongoing control of this weed, chemicals or the Salvinia weevil, and we know many of our residents are concerned about the use of chemicals in the environment and this is why we have decided to test the effectiveness of the weevil,” Mr Robertson said.

The Salvinia weevil is native to South America and has been introduced to areas in Africa, southeast Asia, USA and parts of Australia where Salvinia is a problem and is now a recognised biological control for invasive water weeds.

The weevils have been bred by NSW Department of Primary Industries (DPI) and thousands will be released in the lake at Water Lily Park over three-four weeks.

Each female weevil is capable of laying 300 eggs and, when the larva hatches, it feeds on new buds and eventually kills the plant.

“Whilst the introduction of the weevil is not expected to completely eradicate the weed, we are hoping that it will significantly control its future spread which will make ongoing management in the lake much easier for Council,” Mr Robertson said.

“Many people, including young families, would have been concerned if we had sprayed the lake with chemicals and this option, using an insect to do the hard work, whilst taking longer, is much more acceptable to our residents,” he said.

For more information contact Annie Lewis, Media and Communications Coordinator, on 6626 7320 or 0419 609 189.