Major mosquito outbreak at Sydney water facility crushed

A major mosquito outbreak in south-west Sydney has been contained in a "round the clock" operation that cleared the pests from a significant water facility, Sydney Water said.

In late October, Liverpool Council contacted Sydney Water about a surge in mosquito populations near Chipping Norton, suspected to be linked to the oxiponds at the Liverpool Water Resource Recovery Facility.

Sydney Water collaborated with the council to tackle the issue.

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In less than two weeks, nearly 100 per cent of frogbit - a floating water weed - was removed from the ponds.

Field assessments across ten of the 12 treatment sites showed a 98 per cent reduction in mosquito larvae since November 8.

"In areas where frogbit vegetation persisted, mosquito larvae counts dropped from 400 to nearly zero," Sydney Water water resourse recovery lead Sally Rewell said.b

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"Field surveys have confirmed the amount of airbourne mosquitoes around the plant has reduced by over 90 per cent. We expect a further reduction over the next two weeks."

Specialised machinery was used, including excavators, sucker trucks, boats, and a helicopter, to help remove vegetation, and carry out ground and aerial spraying with larvicides.

"Our crews worked tirelessly day after day to eliminate the mosquito habitats and treat breeding areas," Rewell said.

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Medical Entomology NSW health pathology Associate Professor Cameron Webb said adult mosquito numbers dramatically declined compared to last week's collections.

"This is explained by the ongoing reduction in mosquitoes emerging from oxiponds through weed removal and larvicide treatments," Webb said.

"Larval sampling in the oxiponds recorded a further decline in mosquito abundance and an approximate further 50 per cent reduction from last Wednesday."

More than 50 people worked seven days a week to get rid of the pests, Rewell said.

"This has been a focused operation, with everyone giving their all around the clock," she said.

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