Salvinia weevils being released at Wollombi Brook.

Salvinia is regarded as one of Australia’s worst environmental weeds because of its invasiveness, potential for spread and economic impact.

Salvinia is being targeted for biological control in the Hunter region’s Wollombi Brook.

This is the aquatic weed that choked the Hawkesbury-Nepean River system and stopped recreation activitie sand boating movement in 2004.

The State Government spental most $2m to bring it under control in the Hawkesbury.

NSW DPI, with funding from National Heritage Trust, is conducting research into bio-control with the salvinia weevil Cyrobagous salviniae with encouraging results in the Hawkesbury/Nepean Catchment.

Salvinia is a free floating weed that forms dense mats on water. It consists of many branched horizontal stems which float just below the water surface.

As salvinia matures it becomes more crowded, and the mats overlap and pack together in a concertina-like fashion. Weevil larvae feed inside the stems and adults on buds.

Eventually, the whole mat turns brown and begins to sink and decompose. Using this process, it takes up to 3 years to control an infestation.

The outcome of the research is being applied to the Wollombi Brook in the Hunter, where Cessnock City Council is taking a new approach in the fight against salvinia by using salvinia weevils bred and supplied by NSW DPI, Grafton.

Mr Barry Shepherd, Vegetation Officer and Ms Maria Edmunds, Weeds Officer from Cessnock Council assisted Andrew Petroeschevsky, DPI’s National Aquatic Weeds Coordinator, Glenda Steain, DPI’s State Aquatic Weeds Coordinator and Hunter Councils Weeds Coordinator, Michael Somerville at the release of 3000 salvinia weevils last December.

According to Mr Shepherd from Cessnock Council, this is the first time such a large quantity of weevils have been released in the region to help control salvinia.

'We are using the weevils, a natural predator of this aquatic weed to help control the salvinia in the brook,' he said.

The NSW DPI Salvinia Program uses an integrated approach incorporating physical removal, mapping with chemical control and bio-control using the salvinia weevil.

Contact: Glenda Steain, NSW DPI project officer (State Aquatic Weeds), Richmond on 02 4588 2156.

- GLENDA STEAIN

This story appears in Agriculture Today.