Three weed killers in arsenal for Baldwin Swamp
PEOPLE concerned a fish kill at the Botanic Gardens could be repeated at Baldwin Swamp have been told they can rest easy.
A Bundaberg Regional Council spokesman said weed at the swamp was salvinia, a different species to that starved fish of oxygen at the gardens in January.
"Council is well aware of the long-term issue of salvinia weed at Baldwin Swamp Environmental Park,” the spokesman said.
He said council rangers regularly checked numbers of salvinia weevils, which did not eliminate the weed but prevents it becoming too thick - up to 600mm.
"At present the salvinia is around 50mm thick and able to freely move on the water surface.”
The council is trialling the use of a new environmentally friendly approach to salvinia control, using a floating boom to gradually constrict mats of the weed into smaller sizes, thereby smothering itself.
A salt solution is then applied to the the leaves, effectively killing it without the threat of harm to fish, frogs and native vegetation.
The method has previously been used successfully at wetlands at Sydney Olympic Park.
Although labour intensive, results from the council's initial trial late last year were promising, the spokesman said.
He said it was usually done when funding was available or an area become too thick and choked the waterway, preventing the weed washing downstream to saltwater where it dies.
Through a "good working relationship” the council's is able use Fraser Coast Regional Council's specialised amphibious vehicle to control the weed.
The council also undertakes periodic inspections and control programs on private dams upstream of the wetlands, to help reduce salvinia's reintroduction.
The council originally used herbicides to control it but now employs the salvinia weevil and a machine called the Truxor harvest it.
"This was last carried out in April 2016 with funding from the Burnett Mary Regional Group in partnership with Bundaberg Landcare,” the spokesman said.
"Unlike chemical control, the physical removal of salvinia weed from the water reduces the chance of a mass fish kill as a result of decomposition of dead weed.
The spokesman said a recent upgrade at Baldwin had increased the height of the bridge above the water, removing choke points in the wetlands and allowing the salvinia to move more freely.
He said there were many new and ongoing projects planned for Baldwin Swamp, including the construction of a new lagoon, further tree planting projects, removal of cottonwood tree and construction of a pathway from Que Hee St to the Ring Road.
Salvinia and options to control are documented in the Baldwin Swamp Management Plan, first adopted in 1992, and revised in 1996 and 2003.
A 2017 review of the management plan will include a public consultation phase later this year.