Living With Mosquitoes In The Subtropics

female Predatory mosquito, Toxorhynchites speciosus

female Predatory mosquito, Toxorhynchites speciosus

Question: “Hey Jerry, we’ve found mosquitoes to be a real problem for us on the northside this year. An electronic device has been recommended, do you have any views on it?” Barnaby via Facebook

Reply: Hi Barnaby, I’ve yet to see an electronic device tell the difference between beneficial mosquitoes (our allies) and the pest species. No device is more effective than physical exclusion. And no response is better than adapting your household to living with mosquitoes in the subtropics. I had to do this when I moved here from Sydney in 2003.

I have identified six species of mosquito at Bellis, my home and garden. One of them is the Predatory Mosquito (Toxorhynchites speciosus), a biocontrol. Its larvae are big and they specialise in eating parasitic mosquito larvae (the ones that spread disease). Toxorhynchites breeds in the water-filled trough where I grow my Pitcher plants (Nepenthes spp.), and they have been preventing parasitic, blood sucking mosquito species from breeding in my garden for years. This biocontrol is active from spring to autumn.

Adult Toxorhynchites drink nectar, not blood. They are gentle giants, much bigger than the average mosquito. They’re also noisier and fly more slowly. Often you hear them before you see them. Toxorhynchites has been providing my property with its ecological service for several years. I have trained housemates and visitors to recognise and respect this beneficial creature.

I’ve posted many times on my public Facebook page about the use of biocontrols, including this one. Web-weaving spiders are the best mosquito biocontrol. You can observe how lethal they are in mangroves, their webs strain clouds of mosquitoes out of the air. Yet just a short walk away – where mangroves have been cut down, eliminating spider habitat – and you’ll be eaten alive by mosquitoes.

Electronic mosquito killers cannot detect the difference between beneficial and parasitic mosquito species – like the Predatory Mosquito can. Some electronic devices destroy other valuable biocontrols – like praying mantis, the biocontrols of grasshoppers – and pointlessly massacre harmless winged insect species like moths. I will not have these clumsy contrivances in my home.

Brisbane City Council sprays mosquitoes with a growth regulator, preventing larvae becoming sexually active adults. This chemical significantly reduces seasonal populations of all mosquito species.

Good housekeeping

Simple, good housekeeping in the home and garden dramatically reduce mosquito popluations and problems: gutters that drain, empty pot plant saucers (or fill saucers with sand), keep fish in ornamental pools (I keep Pacific Blue Eye fish), remove fallen palm fronds (which hold water), fit flyscreen to windows, and shut doors.

If you have plants that must be kept damp at all times, have a look at how you can make your own self-watering containers (almost free).

I keep only a few water-holding bromeliads since they are a magnet for mosquitoes. Instead I grow terrestrial bromeliads – pineapples (Ananas spp.), Cryptanthus, Dyckia, Puya and Tillandsia. These do not collect water or attract mosquitoes. I keep  Nepenthes in a styrofoam trough which is a quarter filled filled with water at all times. This is where my Predatory mosquitoes are free to breed.

Make sure your rainwater tank and drains are mosquito-proof. My stormwater infiltration well in the front garden gathers stormwater, allowing it to passively water my front garden faster than mosquito larvae can mature. My rain harvesting home and garden was featured as ‘best practice’ by the Sendzimir Foundation (in Poland) in the latest ‘Guideline for Decisionmakers: Water in the City, Sustainable Development‘ at the European Regional Centre for Ecohydrology, under the auspices of UNESCO.

I apply all the above strategies. Of course there are bursts of mosquitoes, each species breeds in response to the season and weather events, but these bursts pass in a matter of days. I wear appropriate clothing when gardening, I use mosquito repellent, and I keep fly swats in strategic places indoors.

A flowering Utricularia growing amongst waterlilies.

A flowering Utricularia growing amongst waterlilies.

I acquired a species of Utricularia from Suncoast Water Gardens. Utricularia is a free-floating aquatic insectivorous plant with filamentous growth and cute bright yellow flowers in the warm seasons. It feeds on mosquito larvae. Provide a bright position for it to flourish. You can divide plants in late spring and through summer. The down side of this plant is that it doesn’t discriminate between the predatory and blood-sucking species of mosquito larvae.

You can take the fight to mosquitoes by using this trap which employs mosquito breeding behaviour against them. To work this requires a minimum of three traps per hectare – no chemicals are needed. Get your neighbours involved.

Mosquitoes at Bellis:

Predatory mosquito, Toxorhynchites speciosus; large and less common, a beneficial species. Adults feed on nectar, larvae predate larvae of other mosquito species. First photographed on 26.2.12. BCC Mosquito information, see:

Mosquito, Culex quinquefasciatus; a cosmopolitan, medium sized, brown mosquito that favours sewage plants and septic tanks;

Mosquito, Culex annulirostris; the most common and widespread Australian mosquito across Australia. Medium sized, brown, most commonly found in freshwater swamps, especially after late summer rains, when it breeds in temporary grassy pools like roadsides. The most important carrier of Ross River virus in inland Australia and Brisbane, also carries dog heartworm;

Mosquito, Aedes vittiger. A large, pale mosquito with four obvious dark stripes on its thorax, occurring in troublesome waves after heavy rain when it breeds in temporary grassy pools like roadsides. Vicious, persistent and bites through clothes;

Mosquito, Aedes notoscriptus; the commonest Brisbane house mosquito, commonest in winter. Black with white markings on legs and body. Breeds in natural and man-made containers such as tree cavities, gutters, tyres, saucers, bird baths. Vector of Ross River and Barmah Forest viruses and dog heartworm;

Mosquito, Aedes vigilax; common pest species in Brisbane, favours salt marshes and swamps of Boondall Wetland, airport, Tingalpa Creek, Wynnum and Hemmant. Disperses widely, vector of Ross River and Barmah Forest viruses and carries dog heartworm;

Jerry Coleby-Williams
8th April 2015