More than 90% of pesky midges wiped out

The closure of Currimundi Lake since early September as part of Sunshine Coast Council’s midge control program has been deemed a huge success.

Division 3 Councillor Peter Cox said the reduction of midge larvae in the lake by more than 90% was the best possible result council could have hoped for.

“The entrance to the lake was closed off at its high tide level on September 1 to drown midge larvae in an attempt to reduce the adult biting midge population,” Cr Cox said.

“With timing right and results positive, works began at 10.30am today (October 18) to re-open the lake’s entrance, including the removal of some drainage pipes, followed by a 20 tonne excavator digging out the sand berm as the tide dropped.

“Council closes the lake in spring if biting midge larval abundance is increasing to levels that would cause problems in the coming summer.

“A spring closure disrupts the lifecycle of the midge at a critical time by reducing the number of midge that survive to adulthood and lowering the amount of eggs that they lay.

“Before the introduction of the closure program in 2007, larval biting midge abundance was very high in the Currimundi area, averaging 240 larvae per square metre in the lake.

“In the years since then, they have only averaged 54 larvae per square metre, an overall average reduction of 78%.

“Larval levels at the completion of this year’s closure program are lower than at the same stage as all previous closures – currently we are down to 11 larvae per square metre.

“As a result, significantly fewer biting midge complaints are received by council in the Currimundi area compared to a decade ago.”

Cr Cox said the lake re-opening served a dual purpose this year.

“As part of a three-year Australian Research Council (ARC) partnership, council along with the University of Queensland and Sunshine Coast University, used mobile GPS technology to monitor water velocity, height, and basic water quality (e.g. salinity, temp, DO) during the re-opening of Currimundi Lake,” he said.

“This will continue to build on our knowledge of the baseline flow dynamics of the system, particularly during these types of events.”

Fast facts – a timeline

• Up until late 1990s: Research by council showed the lake would naturally close off to the sea regularly, sometimes several times a year and often for several months at a time. Biting midge populations were at low levels which is thought to be due to this natural closure cycle.
• Early 2000s: The lake stopped closing naturally on a regular basis. Midge populations skyrocketed over a few years in the Currimundi area.
• Spring of 2007: Council commenced the lake closure program, replicating what had happened naturally in the 1990s, in response to several years of high numbers of complaints about extreme numbers of biting midge in residential areas within 400m of the lake.