Mosquitos are insects that have immature stages, ie. larvae and pupae, which live in water. The larva is called a wriggler because of its quick movements used to escape danger, and the pupa is called a wobbler. Most mosquito species have immature stages that breathe air from the water surface. Therefore they commonly breed in more or less still water to avoid drowning.
Adults emerge from the water surface, where they immediately start mating, and then they disperse to feed and find new breeding grounds.
Their mouth parts are specialised for piercing, sucking and injecting. Males feed on nectar only but females need proteins from blood for egg development. Eggs are laid near or on water bodies of any size. The breeding cycle, from adult to egg to hatched adult, may be completed in less than a week during warm and abundant conditions.
What health problems do they cause?
Mosquitos have a worldwide distribution and the many species have different requirements of climate, water type and feeding hosts. Total eradication is not possible and mosquitos are of importance in the food chain. However, they can pass on:
- Certain arbo-viruses (such as Ross River virus and Barmah Forest virus)
- Some types of nematode worms (such as dog heart worm and filarial worms in humans)
Allergy and irritation arising from bites may also be severe.
Mosquito-borne disease is not generally transmitted between mosquito generations. The presence or absence of suitable hosts (disease carrying animals or humans) determines whether transmission to and from mosquitos occurs.
Epidemic Polyarthritis is caused by Ross River virus and Barmah Forest virus and these are transmitted by mosquitos only. It occurs only sporadically in Sydney because host animals are less abundant in large cities but it may be more frequent outside cities throughout Australia.
Dengue Fever and Murray Valley Encephalitis are more severe diseases that are very unlikely to be transmitted in Sydney.
Australia was officially declared Malaria-free by the World Health Organisation in 1981 and although there are about one thousand cases of Malaria reported in Australia each year, most of these have been contracted overseas.
For further information on mosquito-related diseases and updates on arbovirus status see the NSW Arbovirus Surveillance and Vector Monitoring Program.
Mosquito Monitoring and Education Program
Council conducts an annual Mosquito Monitoring and Education Program in conjunction with NSW Health, Sydney Olympic Park Authority (SOPA) and other neighbouring local government areas.
The aims of the City of Ryde Mosquito Monitoring and Education Program are:
- To reduce mosquito numbers in residential areas through educating the community on how to prevent mosquito breeding and biting
- To carry out surveys on private and community land as required
- To liaise with government agencies regarding the effectiveness of larvicide programs within the Sydney Olympic Park.
The Program is conducted seasonally from January to at least March and involves weekly trapping of adult mosquitos at six regular sites to obtain data on population sizes of local mosquito species and to acquire specimens for testing of mosquito-borne viruses.
The Program also involves:
- Carrying out larval surveys of watercourses, and carrying out treatment with biological larvicide as required
- Investigating nuisance reports from residents
- Conducting public displays in libraries and providing information on the City of Ryde’s website and in the local media
- Reporting annually to Council and NSW Health.
Report Mosquito Breeding Sites
- Call Council's Customer Service Centre on 9952 8222
- Call the Environmental Monitoring Officer on 9952 8197
Local Mosquito Species
The mosquitos that have shown to be most prevalent in the Ryde area are the Saltmarsh Mosquito (Aedes vigilax) and one species of the Freshwater Mosquitos, (Aedes notoscriptus).
The Saltmarsh Mosquito (Aedes vigilax) is very aggressive. It breeds in Homebush Bay saltmarshes and other low lying, tidal locations along the Parramatta River. During the summer months, the Saltmarsh Mosquito rapidly increases in numbers and can disperse 5 - 10km with wind assistance. They can go as far north as Macquarie Park.
The Sydney Olympic Park Authority (SOPA) is responsible for reducing the numbers of emerging Saltmarsh Mosquitos in the Homebush Bay area with ground and aerial, larval spraying of their habitat. Each larvicide treatment normally reduces larval numbers by more than 90%.
To date there has been no sign of productive Saltwater Mosquito breeding along the City of Ryde foreshore.
Several freshwater mosquito species, including the common Domestic Mosquito (Aedes notoscriptus) can be found in local residential environments - e.g. in puddles (after rain), stagnant drains and creeks, blocked roof gutters, ornamental ponds and water features, rubbish and containers, and dirty and partly empty swimming pools. Freshwater species normally travel only 50 - 100m from their breeding site.
Keeping Mosquitos at Bay
Here are some precautions to protect yourself from bites and to minimise mosquito breeding around your home.
- Use DEET® or Picaridin® based repellents and apply to exposed skin when:
- Venturing outdoors at dusk or dawn. (This is when most mosquito species are looking for a meal)
- Venturing close to wetlands and irrigation and bushland areas that are natural breeding grounds
- Fit fly screens on windows and doors around your home
- Fit mosquito nets onto beds and prams as an additional protection.
Around Your Home
The mosquito breeding cycle may be as short as one week and eggs are laid in the smallest bodies of water:
- Chlorinate and circulate swimming pools, as dirty and partly filled pools may cause intensive mosquito breeding. Tip out children’s pools regularly
- Change water in birdbaths and pet bowls at least weekly
- Keep water features circulating to drown larvae
- Stock ponds with larvivorous fish (tadpoles do not eat larvae)
- Check drains and roof gutters for blockages and clean them out regularly. Pits may be treated with chlorine / bleach
- Put insect netting on inlets to water tanks and containers or seal them
- Remove any water holding vessels around your property, or turn them upside down
- Remove pot plant saucers or fill them with sand
- Keep lawns short and trim shrubs regularly – as mosquitos shelter in these areas.
Find out more
To obtain general advice, an update on current nuisance levels or arrange for an inspection by our staff call Council's Customer Service Centre on 9952 8222.