DPI’s salvinia bio-control facilities at Grafton in big demand

The invasive waterweed salvinia is coming under increasing attack from small weevils from the salvinia biological control rearing facility at the NSW Department of Primary Industries (DPI) Grafton Research Station.

"Forty-litre tubs of salvinia infested with thousands of weevils have been sent across the State to attack outbreaks of the waterweed on rivers and dams," said DPI’s regional weeds coordinator Rod Ensbey.

"So far this year 165 tubs from Grafton have been introduced to 32 sites infected with salvinia from Wollongong to the Queensland border," he said.

"The NSW DPI Weeds Unit at Grafton has worked with 18 local control authorities who are actively using the salvinia bio-control service to successfully control salvinia outbreaks."

Mr Ensbey said the biological control agent, Cyrtobagous salviniae, commonly known as the salvinia weevil, is native to South America and feeds exclusively on the aquatic weed salvinia.

"With suitable climatic conditions the weevil can reduce entire mats of salvinia to a few scattered plants in 1-2 years," he said.

"In suitable climates the weevil provides a more cost effective and long term solution to herbicide and physical removal. However, in some conditions it can take years for weevil populations to build up to a level where they can provide control; people should not expect to see immediate results." 

Mr Ensbey said the expanded facility at DPI’s Grafton Research Station was constructed as part of a Natural Heritage Trust project to improve the distribution of the salvinia weevil in NSW.

"Six above-ground swimming pools are now used to breed the weevils," he said.

"Each pool is filled with weevil-infested salvinia and staff have the busy task of ensuring that enough fresh salvinia is supplied to keep the populations growing.

"Weevil-infested salvinia is then taken from the pools and released into salvinia infestations."

Mr Ensbey said salvinia is a floating aquatic weed that originates from South America. It was introduced for ornamental purposes but has since spread to much of Eastern Australia’s streams.

"It is a Weed of National Significance and has devastating impacts on waterways where it can form dense floating mats that cover the entire water surface," he said.

"Such mats can cause losses of fish and bird life, clog irrigation equipment, increase evaporation and can damage infrastructure during flood events."

According to Mr Ensbey the weevil is most successful in the warmer NSW north coast region.

"In climates south of Taree its effectiveness is reduced but with careful release strategies it can provide an effective control option as far south as Sydney," he said

Landholders who have salvinia infestations are advised to contact their local government weeds officer for further advice.

Further reading

Weed profile: Salvinia