What the Shire is doing to mitigate mosquitos

Published on 17 June 2020


The Shire of Broome would like to provide more information on the mosquito nuisance issue occurring in town at the moment.

Results of adult mosquito trapping undertaken by our Environmental Health Officers show the species of mosquito we are currently experiencing is the Aedes vigilax - a saltmarsh / brackish water-breeding mosquito. Large hatch-out events of this type of mosquito generally occur as a result of higher tide events.

Officers believe this recent hatch-out is likely to have occurred as a result of the spring tides around the new moon of late May.

The Shire is acutely aware of the push from the public to fog to reduce the current adult mosquito population in Broome.

While fogging is a part of our suite of response options to manage mosquito numbers, it is considered the option of last resort as it poses the most risk to the environment.

The Shire utilises integrated pest management principles to respond to mosquitoes, which includes surveillance (larvae and adults), a sentinel chicken bleeding program, community education, larviciding and, in certain circumstances, adulticiding. 

Ideally, fogging should only be used where there is an imminent public health risk associated with mosquito-borne disease transmission, not simply to reduce nuisance.

The primary reason is the chemical used in fogging is not target-specific, therefore all flying insects the fogging cloud comes into contact with will be killed, including bees and dragon flies. It is also lethal to fish, so any drift over wetlands / mangroves poses a relevant risk.

Residents growing organic crops / gardens are also impacted.

Additionally, there is no residual effect, meaning that once the cloud dissipates, there is nothing stopping other mosquitoes reoccupying a particular space – even within hours.

As a precaution, our sentinel chicken bleeding program has been escalated to checking on a fortnightly basis, as opposed to our usual monthly program for this time of year.

Based on calculations, the mosquitoes currently impacting the townsite will likely have hatched around two days either side of May 30, with the average lifespan of mosquitos being 2-3 weeks.

The current trapping program has indicated numbers are in decline, meaning the current lifecycle of the recent large event hatch-out seems to be coming to an end.

Whilst the number of mosquitoes is certainly a nuisance, the use of fogging is ill-advised at this time.

Environmental Health Officers are continuing to monitor the situation and will advise if any change occurs.

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