All about Mosquitoes
There are a number of suburbs that are in very close proximity to large mosquito breeding sites. After the adult mosquitoes have emerged they leave the breeding sites to seek out food and resting places such as backyard gardens, reserves and natural remaining bushland. Once mating has occurred, the female will seek blood meals and then return to the breeding grounds to lay her eggs. Once her eggs have been deposited she will return back to feed and rest in these types of areas over her entire lifetime. Males will feed on nectar and plant juices but do not seek blood.
Areas that have particularly thick foliage and shade may attract higher numbers of mosquitoes. These types of areas that are close to breeding sites will inevitably attract higher numbers of adult mosquitoes.
The average life span for an adult mosquito can be between two to four weeks although it can be longer in certain conditions and cooler months. Males usually die before the females.
Some species travel only short distances from their breeding sites, whilst others like the Aedes vigilax that breeds in the South West during the summer months has been known to travel more that 20km from its breeding sites. This is why some people who do not live close to breeding sites are still at risk of being bitten by mosquitoes that carry disease and also find them in nuisance levels. Within 3km of a breeding site, mosquitoes of most species in the Leschenault and Geographe Regions will move freely and be likely to cause nuisance at certain times.
In 2019 we conducted a study marking 464,000 mosquitoes and tracing how far away we trapped them. See the results here
The majority of mosquito species are most active at dusk and dawn. Some species found in the south west remain somewhat active throughout all times of the day. It is important to apply a personal repellent to all exposed skin when outdoors in mosquito prone areas.
Information on the common mosquitoes within WA is available on the WA Department of Health website: https://ww2.health.wa.gov.au/Articles/A_E/Common-mosquitoes-in-Western-Australia
Yes. Fish, aquatic beetles and aquatic bugs all feed on mosquito larvae. They can be a great help with controlling mosquito larvae within permanent water bodies. Spiders are also a natural predator for adult mosquitoes.
This behaviour, particularly clustering together or swarming, is more consistent with midge and not typical of mosquitoes. If the insects aren’t biting they are most likely midge, which do not have a disease transmission risk. Ensure your doors and windows are screened and kept closed to minimise the risk of mosquitoes and midge entering your home.
All about our management efforts
The majority of treatments that are undertaken are targeted on the larval stage of the mosquitoes lifecycle not the adult stage. These treatments are carried out once hatching or larval activity has been detected via breeding site surveys. The aerial treatments are not scheduled as such but are undertaken and timed to result in the highest possible reduction of potential mosquito numbers. Once adults have emerged they disperse over a large distance and make adult mosquito management very difficult.
Generally local government does not utilise adulticiding (fogging) as a main method for mosquito reduction. Adulticiding has not proven to be very effective in our area and the most effective treatment method is larviciding. Occassionally we will utilise adulticiding at times of very high disease risk or when mosquitoes are in extreme numbers. The areas that are targeted with adulticides will usually be those adjacent to breeding sites or particular areas that harbour large numbers of adult mosquitoes.
Adulticiding is non-specific (ie. it kills other beneficial organisms and is also heavily dependent on wind conditions and requires winds of less than four knots). The chemicals are lethal to aquatic life (especially fish), can be toxic to birds and may cause eye and respiratory irritation to humans. For these reasons the City uses adulticiding (fogging) sparingly and as a last resort.
The local government authorities’ mosquito management program is largely successful in reducing and maintaining acceptable numbers of mosquitoes. Due to extensive breeding areas and larval densities, total eradication is not possible, or environmentally desirable, and the program aims for the best kill rates possible. Weather conditions can also impact on the effectiveness of treatments particularly if storm surges are received immediately after larvicides are applied. It is important for residents and visitors to remember that personal protective measures are required in the Geographe Bay Region and greater south-west.
All larvicides used are approved by the Australian Pesticides & Veterinary Medicines Authority. The approval process requires rigorous evaluation of the efficacy of the product in killing mosquito larvae when used appropriately. Ensuring the safety of the product if it is applied to water sources used by animals, such as livestock and birds. The Department of Health regularly undertakes calibration of the equipment on the helicopter to ensure the product is applied at the rate specified on the label. Where the wetlands involved were Ramsar listed, those covered by international treaties governing protected wetland ecosystems, Council sought approval from the Federal Department of Environment & Heritage to carry out the larvicide program.
The most commonly used larvicides in the south west are those containing either S-methoprene or Bacillus thuringiensis var. israelensis (Bti). Neither of these products are considered toxic to humans.
S-methoprene is an insect growth regulator, this mimics the juvenile hormone and prevents the adult mosquito emerging. It enables the larval and pupal stages of the mosquito to remain in the food chain as a food source for other animals.
Bti is a naturally occurring soil bacterium that produces endotoxins and spore, commonly formulated into a granule using corn cob grit. Mosquito larvae are killed when they ingest the endotoxin. This is only toxic to mosquito larvae and does not harm other aquatic, marine or terrestrial fauna.
More information is available on product stockists websites including the product labels and safety data sheets.
- Dispose or empty regularly all water holding containers
- ensure gutters are clean, draining freely and do not hold stagnant water
- Avoid over watering lawns and sprinkler run off into storm water drains that create permanent pools of water in the storm water drain
- Fit mosquito proof cowls on the vent pipes of septic systems
- Screen rainwater tanks to prevent mosquitoes entering and laying their eggs on the water surface
- Refer below to ‘How do I reduce mosquitoes around my home’ for more tips
Use an insect repellent containing DEET (diethyltoluamide), picaridin or Oil of Lemon Eucalyptus. As a general rule, the greater the percentage of DEET or picaridin, the longer the product will remain effective. Always read and follow the label instructions. Further information is available on the WA Department of Health website – https://healthywa.health.wa.gov.au/Articles/F_I/Insect-repellent
https://ww2.health.wa.gov.au/Articles/N_R/Personal-insect-repellents
- Screen outdoor patios and sitting areas with fly screens and doors
- Use a fan in outdoor areas to create an air pressure change that repels mosquitoes
- Reduce the number of lights used at night in outdoor areas and change to yellow or to low fluorescence globes
- Use outdoor ‘bug zappers’ on patios and outdoor sitting areas
- Cut, mow or reduce the amount of excess moist garden foliage around your home. Mosquitoes like to rest in these areas during the day
- Use mosquito coils, lamps or candles that burn citronella to repel mosquitoes
- Apply a residual insecticide product (one that remains on a surface for 1 – 2 weeks) on patio and house eves, door and window sills, paved areas and some garden areas. The adult mosquitoes (and other insects) will perish after landing on treated areas. Applications that are mixed in a garden or hand sprayer are the most effective. Ensure you read the product storage and handling instructions carefully and use the correct equipment specified when applying any products
- Refer to the question above for more tips on how to prevent breeding around the home.
All about Mosquito Borne Diseases
There are a number of suburbs that are in very close proximity to large mosquito breeding sites. After the adult mosquitoes have emerged they leave the breeding sites to seek out food and resting places such as backyard gardens, reserves and natural remaining bushland. Once mating has occurred, the female will seek blood meals and then return to the breeding grounds to lay her eggs. Once her eggs have been deposited she will return back to feed and rest in these types of areas over her entire lifetime. Males will feed on nectar and plant juices but do not seek blood.
Areas that have particularly thick foliage and shade may attract higher numbers of mosquitoes. These types of areas that are close to breeding sites will inevitably attract higher numbers of adult mosquitoes.
The average life span for an adult mosquito can be between two to four weeks although it can be longer in certain conditions and cooler months. Males usually die before the females.
The majority of treatments that are undertaken are targeted on the larval stage of the mosquitoes lifecycle not the adult stage. These treatments are carried out once hatching or larval activity has been detected via breeding site surveys. The aerial treatments are not scheduled as such but are undertaken and timed to result in the highest possible reduction of potential mosquito numbers. Once adults have emerged they disperse over a large distance and make adult mosquito management very difficult.
Generally local government does not utilise adulticiding (fogging) as a main method for mosquito reduction. Adulticiding has not proven to be very effective in our area and the most effective treatment method is larviciding. Occassionally we will utilise adulticiding at times of very high disease risk or when mosquitoes are in extreme numbers. The areas that are targeted with adulticides will usually be those adjacent to breeding sites or particular areas that harbour large numbers of adult mosquitoes.
Adulticiding is non-specific (ie. it kills other beneficial organisms and is also heavily dependent on wind conditions and requires winds of less than four knots). The chemicals are lethal to aquatic life (especially fish), can be toxic to birds and may cause eye and respiratory irritation to humans. For these reasons the City uses adulticiding (fogging) sparingly and as a last resort.
Some species travel only short distances from their breeding sites, whilst others like the Aedes vigilax that breeds in the South West during the summer months has been known to travel more that 20km from its breeding sites. This is why some people who do not live close to breeding sites are still at risk of being bitten by mosquitoes that carry disease and also find them in nuisance levels. Within 3km of a breeding site, mosquitoes of most species in the Leschenault and Geographe Regions will move freely and be likely to cause nuisance at certain times.
Yes there are a number of species of both fresh and saltwater breeding mosquitoes that are known carriers and transmitters of Ross River virus and Barmah Forest virus. If you think you have become unwell after being bitten by a mosquito you should visit your GP to seek medical advice.
The local government authorities’ mosquito management program is largely successful in reducing and maintaining acceptable numbers of mosquitoes. Due to extensive breeding areas and larval densities, total eradication is not possible and the program aims for the best kill rates possible. Weather conditions can also impact on the effectiveness of treatments particularly if storm surges are received immediately after larvicides are applied. It is important for residents and visitors to remember that personal protective measures are required in the Geographe Bay Region and greater south west.