Types of mosquitoes
There are a number of different mosquitos that can impact you, your family and your pets.
Some mosquitoes breed quickly after rainfall, especially the common banded mosquito (Culex annulirostris), the most abundant freshwater mosquito in South East Queensland.
This mosquito breeds in shallow freshwater pools as well as in grassy drains and depressions, particularly in rural areas or suburbs with open space, which includes most of Brisbane.
The common banded mosquito is considered the most effective carrier of Ross River virus in South East Queensland. It also carries Barmah Forest virus. Other freshwater breeding mosquitoes can also carry these viruses, as well as heartworm, which affects dogs and cats.
Council controls Culex annulirostris and other mosquitoes on public land, however private landowners are responsible for the control of mosquitoes on their land.
In summer almost every residence in Brisbane provides habitats for the common backyard mosquito (Aedes notoscriptus). These mosquitoes breed in natural containers such as tree cavities and bromeliads, as well as man-made containers such as pot plant trays, bird baths, discarded tyres, garden rubbish and gutters. They also breed in unmaintained swimming pools and poorly-screened rainwater tanks.
In summer, adults can be abundant about a week after rain has filled containers causing their eggs to hatch. This species also occurs in winter in well-watered gardens and can transmit dog heartworm.
The Dengue mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus) are container-breeding mosquitoes but do not currently occur in Brisbane.
Saltmarsh mosquitoes (Aedes vigilax) breed in saltmarsh and mangrove habitats in Brisbane. These areas cover much of coastal Brisbane from the Pine River in the north to Tingalpa Creek in the south. The Boondall and Tinchi Tamba Wetlands are prime habitat for this mosquito.
The saltmarsh mosquito is Brisbane’s most significant mosquito pest due to:
- huge numbers simultaneously hatch after trigger events such as rain or high tides
- adults are highly mobile and disperse inland for five to 10 kilometres
- female mosquitoes have highly aggressive biting behaviour
- they have the capacity to carry Ross River and Barmah Forest viruses.
Saltmarsh mosquitoes can be a particular problem during times of low rainfall as their eggs are conditioned to hatch in greater numbers after a period of drying out.
Rain over 40 mm or high tides over 2.4 m can trigger a hatching event and biting activity can be expected approximately 10 days later. The adults live for one to two weeks.
Adult female and eggs
Adult female emerges and her first batch of eggs is laid. The females then disperse (up to 10 Kilometres) in search of a blood meal with the aim of returning to the saltmarsh to lay more eggs. The female saltmarsh mosquito lays her eggs on damp soil at the base of saltmarsh vegetation around the high tide mark and at the edge of impounded pools in mangroves. These eggs dry and become dormant. They hatch weeks to months later when submerged by tide or rainwater that refill the depressions. Adult saltmarsh mosquitos only live for 1-2 weeks.
Larvae are aquatic and develop into pupae in as little as 5-6 days.
This is the only time the mosquito is vulnerable to Council’s eco-friendly treatments. Council needs to treat the saltmarsh mosquito larvae in their breeding pools before they emerge with either Bti (Bacillus thuringiensis israelensis) or Methoprene:
- Bti (Bacillus thuringiensis israelensis) - only effects larvae for the few days before they pupate and the larvae need to ingest it.
- Methoprene - works by stopping the larvae developing into pupae properly.
These products only target the larvae and are safe for other insects, the environment and humans. They are sprayed by helicopter with ground support by quad bike spray teams.
There are usually only a few days available after a hatching event to successfully control the larvae with these products.
If not treated, in 1-2 days pupae develop into flying adult mosquitoes.
The female will begin life by laying the next generation of eggs and so the cycle continues.