Midges are native flying insects a few millimetres in size. They live around the lake edges where they tend to swarm at dusk and dawn prior to laying eggs in lake water.

In the past the lakes were important to the sewage treatment process. Our modern plant now processes the wastewater upstream so that the treated effluent that enters the ponds is of a much higher quality. The role of the lakes is now to “polish” the effluent by removing any remaining bacteria and to provide storage following heavy rain. This means they are more like natural lakes and oxygen levels remain high day and night. As a result the lakes support more aquatic life, including small fish and insects. One of the first organisms to colonise the lakes are midges.

The midge larvae, also known as bloodworms live and feed on the lake floor. The larvae are an important part of the ecology and consume organic matter on the lake floor.

While midges are quite harmless, they can become a nuisance when present in high numbers. Especially at night they can be attracted to porch and outside lights in the neighbourhood. The problem is normally localised and more likely in spring or summer when air and water temperatures are warmer. In order to avoid this nuisance midge numbers at the lakes need to be controlled.

Midge pesticide trials

Over the 2002/2003 summer we monitored the number of midges and midge larvae in the lake now and are carrying out further sampling of the lake bottom to understand the situation better. In seeking a long term solution to the problem we undertook consultation with the neighbourhood. 

After feedback from residents, we carried two trials of pesticides to reduce the number of midges around the lake. We took all possible precautions to ensure that no birds or wildlife were harmed or distressed during the trials. A boom was been placed around the outlet pipe to prevent pesticide escaping through the outfall to sea. This was inspected daily to ensure that it was effective.

In May 2003, a decision was made to apply to the Auckland Regional Council for a resource consent to apply Methoprene as a primary control and Agnique as a secondary control, if required in the future.

Midge newsletter 1 (109 KB)
Midge newsletter 2 (1.35 MB)
Midge newsletter 3 (1.03 MB)