In South East Queensland, local, state and national authorities all play a role in mosquito control. Many of these bodies run mosquito control programs and they carry out activities to:
- locate and map potential breeding sites in coastal and freshwater areas
- monitor sites for mosquito larvae after heavy rainfalls and high tides
- proactively treat mosquito-prone areas with larvicides and insecticides (targeting mosquitoes at different stages during their life cycle)
- re-survey sites and water sources to confirm that a treatment is effective.
When authorities detect mosquito larvae at a site they may spray chemicals known as larvicides to selectively kill certain species before they mature into adults. Larvicides can be applied by airplane or helicopter (useful for larger sites) or by ground vehicle.
Two larvicides are commonly used because they have minimum impact on other organisms in the environment:
- Bti - a toxin from the bacteria Bacillus thiurengensis israelensis, is a host-specific toxin that only affects the larvae of mosquitoes and very closely related flies. It does not affect fish, amphibians or other aquatic invertebrates like crustaceans or dragonflies.
- S-methoprene - an insecticide that mimics insect growth hormones and disrupts a mosquito's metamorphosis from larva to pupa to adult.
Surveys routinely indicate that more than 95 % of the larvae at a site are eliminated by larvicide treatments, though the success rate will depend on:
- the life cycle development stage of the mosquito population
- overhanging vegetation or canopy cover that can shield breeding sites from treatments
- wind drift that carries airborne insecticide sprays away from a targeted site
- Prevailing weather (e.g. rain)
For example, Bti is very effective against mosquito larvae in the first two sub-stages of larval development. However, it is less effective in later larval sub-stages or on the pupae stage. Operators have a very narrow window (usually only two or three days) during which they can apply Bti effectively.
Adult mosquito control
Spraying chemicals that target adult mosquitoes is known as fogging - a practice that is less effective than spraying larvicides. Although fogging kills adult mosquitoes in a specific location, nearby mosquitoes can quickly repopulate an area in a short time. Insecticides that kill adult mosquitoes often affect other organisms (such as insects and butterflies) and for this reason, larvicides are preferred over fogging.
Because fogging is only effective in the short-term and may damage non-target organisms, councils often do not routinely carry out adult control but prefer to eliminate mosquitoes before they become adults.
Mosquitoes that develop in water-holding containers (whether natural or artificial) are known as container-breeding mosquitoes. Most local councils in South East Queensland do not carry out control for container-breeding mosquitoes on private or commercial premises. The Australian government also monitors first ports of entry, such as airports and sea ports, and intercepts exotic, container-breeding mosquito species, such as Aedes aegypti and Aedes albopictus.
Exotic mosquito control
Local, state and national authorities conduct surveillance to detect the presence of Aedes aegypti and Aedes albopictus. These exotic mosquito species carry dengue and Zika virus and are difficult to eliminate once established.
The Department of Agriculture and Water Resources also monitors airports and sea ports to ensure these species mosquitoes do not enter Australia by air or sea.
Queensland Health and local governments also carry out ovitrapping activities where they collect as many container-breeding mosquito eggs as possible, then use a novel genetic technique to detect the presence of exotic eggs.
Mosquito control authorities
- Queensland Health Communicable Diseases Branch
- Mosquito Control Association of Australia (MCAA)
- Mosquito and Arbovirus Research Committee, Inc. (MARC)
- Zika Mozzie Seeka - a community volunteer program to conduct bio-surveillance for exotic mosquitoes in your own yard.
- NSW Arbovirus Surveillance & Vector Monitoring Program