SINGAPORE - National water agency PUB is greasing drain walls to trap midges when they land to rest, and placing an extra kilometre of netting on reservoir dykes to capture adult midges that might be blown into residential estates.

These measures, which are being introduced in local reservoirs here, are in addition to the PUB's current suite of weapons to combat the perennial midge problem.

The measures target the current dominant midge species in Singapore, which is considered rare, Minister for the Environment and Water Resources Masagos Zulkifli said in Parliament on Monday (Sept 2).

Midges have been swarming at Pandan Reservoir and are causing a nuisance to residents living nearby.

Responding to questions from three MPs on the measures being put in place to counter the problems at Pandan Reservoir, Mr Masagos said the current outbreak is different from the last emergence of midges there in 2016.

Unlike common midges, he explained that the rare species hides in drains in the day and swarms above drains in the evening.

"Midges neither bite nor spread diseases. But they pose a nuisance to the public when they swarm in large numbers, and being weak flyers, get blown by wind into the surrounding residential estates," Mr Masagos said.

He attributed the fast growth of midges this year to an unusually hot July, the second warmest recorded since 1929.

"With climate change, we will experience more extreme weather, which will have a corresponding response from nature," Mr Masagos said.

He added that midges have appeared from time to time in several reservoirs, including the Bedok, Punggol, Serangoon, Poyan, Tengeh, and Marina reservoirs, as well as Punggol Waterway.

Swarms have also appeared at Pandan Reservoir since the late 1970s.

But the PUB has since mid-July this year increased the frequency and dosage with which they apply a biological liquid larvicide in the reservoir, to kill midge larvae.

And in keeping with the usual measures the agency employs, the frequency of fogging and misting around the reservoir dyke and surrounding vegetation has been stepped up, to kill adult midges.

The midges are also kept near the reservoir area by the bright lights, so the PUB can target swarms by fogging at these spots. Bright spotlights have been installed at the Pandan Reservoir pumping station. These are turned on at night, to attract adult midges as they emerge from the reservoir.

Mr Masagos noted that the problem of midges is very much a struggle of man versus nature.

"Man has never been known to win - we can only suppress, and do our best, but we have to live with them, as we are the ones who are intruding into the midges' habitats," he added.

"There is a limit between killing enough midges, and killing so much of everything, that we end up killing ourselves. There is also a limit to which these measures can mitigate the issues that residents are facing," he said.

Ms Foo Mee Har (West Coast GRC) asked Mr Masagos about the efficacy of the PUB's various measures to deal with midges, and whether there might be any health risks that residents might be exposed to with sustained periods of fogging in the area.

Mr Masagos said the pesticide used for fogging, Permethrin, was evaluated by the World Health Organisation, and has been certified safe to use.

The pesticide is also applied at ratios that are safe for humans, including the operators of the fogging machines. The larvicide introduced into some reservoirs is also a naturally occurring material that targets the digestive system of midge larvae, and is not harmful to humans.

The PUB's additional measures to keep midges in check will continue until the swarms of midges are gone.