Study and Mitigation of Midge Population Problem at Bedok Reservoir since November 2025

Mr Gerald Giam Yean Song asked the Minister for Sustainability and the Environment (a) whether the midge population at Bedok Reservoir from since November 2025 is larger compared to previous years; (b) whether studies have been conducted on midge resistance to current biological larvicides; (c) whether there are plans to rotate chemical controls; and (d) what is the measurable effectiveness of LED diversion in reducing midge counts in residential units.

The midge population at Bedok Reservoir in the period from November 2025 to January 2026 is higher compared to previous years.

The Public Utilities Board's (PUB's) data shows that the current biological larvicide remains effective. PUB, thus, does not have plans to rotate its chemical controls. In response to the higher midge population in this period, PUB has increased the application of biological larvicide and the frequency of fogging.

Light-emitting diode (LED) spotlights concentrate the midges which allows for more targeted fogging. For this reason, LED spotlights remain a useful part of the suite of measures, even though PUB has not been able to quantify their effectiveness.

PUB will continue to monitor the midge situation at our reservoirs closely and review the measures as needed.