Each summer, mosquitoes make their presence felt as their biting behaviour disrupts our outdoor activities. Australians spend thousands of dollars annually on lamps, traps, candles, sprays, coils and personal insect repellents in an attempt to keep mosquitoes at bay. Unfortunately, they are unaware of the potential adverse health effects of many of these products.

Canadian researchers who tested 16 personal insect repellents found that those containing diethyl-meta-toluamide (DEET) were, by far, the most effective in deterring mosquitoes⁷. Products available locally contain this ingredient which is believed to work by blocking the carbon dioxide and lactic acid receptors that enable female mosquitos to locate hosts¹⁸ . Although it has been used for over 40 years, it may cause eye, skin and mucous membrane irritation and central nervous system disturbances, particularly in children¹³ . While the US EPA¹⁷ has approved DEET for use on children over two months old, the Canadian Ministry of Health Promotion4 recommends that children under 2 years of age should not generally have DEET applied to either their clothing or their skin. 

Most insecticidal mosquito control products available locally contain either pyrethrin or pyrethroid compounds, together with the synergist piperonyl butoxide1. Both pyrethrins and pyrethroids may cause skin, eye and respiratory tract irritation and allergic reactions^{11, 14}, while piperonyl butoxide, a possible carcinogen¹⁵, may cause skin irritation and moderate gastrointestinal symptoms in sensitive people⁵.

Safer alternatives

Since mosquitoes lay eggs in standing water, the greatest potential for reducing mosquito numbers lies in eliminating stagnant water sources. Because as little as a tablespoon of water is sufficient for egg hatching¹⁰ and larvae take at least one week to develop into the pupae from which adults emerge¹², taking the following actions weekly will significantly reduce mosquito breeding^{3, 9} :

• Remove from the outdoor environment any objects, including children’s toys, that may hold even small amounts of water.
• Dispose of rubbish in which water may pool
• Clean out gutters
• Empty children’s wading pools when not in use
• Change water in bird baths and animal troughs which cannot be removed
• Dump water off pool/spa covers, tarps and plastic sheeting
• Remove water that has collected in the centre of bromeliad plants. Ideally, avoid planting bromeliads in mosquito-prone areas.
• Repair leaking garden taps
• Cover water tank openings with flyscreen
• Fill holes in which puddles form
• Clean out garden ponds, as floating debris provides mosquito breeding sites

As mosquitoes cannot breed in moving water, installing a fountain, aerator or waterfall feature will make ponds less attractive to them. Stocking ponds with fish such as guppies and goldfish, which feed on mosquito larvae⁶, and attracting to the garden adult mosquito predators such as frogs, lizards, dragonflies and some birds, may also help to reduce mosquito numbers.

To minimise contact with those mosquitoes which are present, limit outdoor activities at dawn and dusk when mosquitoes are normally most active. When outdoors, avoid being near carbon dioxide-producing open flames and wear thick, light coloured, loose fitting clothing, as mosquitoes are attracted to dark clothing and can bite through thin, tight fitting garments¹⁰. A natural mosquito repellent such as one containing citronella, catnip or lavender essential oil, may be used, provided that the person is not sensitive to these oils¹⁶. Avoid wearing creams/lotions/fragrances with a fruit or floral aroma, as such scents attract mosquitoes².  Cover baby strollers with mosquito netting.

Locate mosquito repellent plants, including balm of Gilead (Cedronella canariensis), fennel Foeniculum vulgare) and “mozzie buster” pelargonium (Pelargonium citrosum “Van Leenii”) around doors, windows and outdoor living areas¹⁹. To keep mosquitoes outside, ensure that all doors and windows are protected with tight fitting flyscreens that are in good condition.

Finally, talk with neighbours about implementing mosquito control measures on their properties. While the actions of a lone household will not create an isolated mosquito-free zone, the efforts of a whole neighbourhood can successfully reduce mosquito numbers.