For all our concerns about dwindling insect populations and accelerating species extinction rates, there is one creature that fails to capture our affection writes Megan Backhouse (The Age). A tiny slip of a thing, it’s irritating at best and deadly at worst: the mosquito. It never fails to shift the mood. The more there are, the more miserable we become.
Australia has about 300 of the 3500-odd mosquito species in the world, and I could swear that this summer in my garden – near an especially mozzie-prone Bellarine Peninsula wetland – I have had all 300 types.
I am not alone. In January the state government’s acting deputy chief health officer issued a health warning about mosquitoes and Ross River virus in south-west Victoria, saying “recent weather and water conditions in the Surf Coast, Geelong and Bellarine Peninsula areas are favourable to mosquito biting and breeding”, while people in other areas too have reported more mosquitoes than usual.
A wetter-than-average January and February is thought to be the cause, resulting in more areas of stagnant water in which mosquitoes can reproduce. But that’s not the only thing that can encourage mosquitoes. Scientists are warning global warming can also increase numbers, as can the displacement of the birds, bats, dragonflies and other insects that consume them.
All of which points to the idea that how we live – including how we garden – can influence how many mosquitoes we have to endure. In the latest issue of the Australian landscape architecture journal Kerb, American architectural designer Angeline C. Jacques describes how entangled are the lives of mosquitoes and people. She calls it a “coevolution” story. The mosquito, she writes “exists in its current state only due to a history of adaptation to human action and expansion”.
Jacques describes how mosquitoes have been spread around the world over centuries by cargo ships and how a new mosquito subspecies evolved to thrive in the human-built environment of an underground train station.
She also details how numerous genetics labs around the world are researching ways in which people might influence mosquito numbers in another way: by unleashing gene drive options to eliminate some of the most disease-spreading types.
Any discussion about the deliberate extinction of an entire species, however, opens up all sorts of questions about the ecological role of mosquitoes and also about human value systems. Although mosquitoes are not key pollinators of important crops in the way that bees are, studies have shown how they do have ecological interactions with plants including pollination.
While all this plays out, a more immediate – not to mention less contentious move – is to implement measures to simply reduce numbers in your own patch.
First, scour your garden for any areas of standing water (blocked gutters, unsealed rainwater tanks and self-watering planters, say) where female mosquitoes might lay eggs. Even a bottle lid’s worth of water has been found to support mosquito reproduction, and sometimes just the moisture that collects in long grass and other plants can do it.
Birdbaths are also obvious contenders, so make sure you empty and refill them at least once a week as even if mosquitoes have a chance to breed in this time they won’t have yet emerged as adults. For ponds, consider adding a pump to aerate the water and keep it moving. Adding fish, such as native pygmy perch, also helps, while some of the birds and insects that ponds attract, such as dragonflies, can also make a dent on mosquito numbers. Microbats also consume mosquitoes as part of their diet (some say hundreds an hour) and if your garden doesn’t contain old trees with the sort of natural hollows in which these bats can roost, add a small specially made box to attract them.
Watering less is another strategy. Selecting Mediterranean-climate plants that can cope without supplementary water in dry hot summers reduces the likelihood of damp spots where mosquitoes can breed.
Some plants are considered to be mosquito repelling such as the pointedly named Leptospermum liversidgei “Mozzie Blocker”, a native, lemon-scented shrub, and many Mediterranean-climate ones including basil, rosemary, thyme, alliums, catnip, scented geraniums and lavender, the fragrances of which are thought to confuse and deter mosquitoes. Though I grow many of these plants and have not noticed any marked impact on numbers.
The move that has had the most success in my garden is more prosaic. I have taken to dragging out an electric pedestal fan when sitting outside at dusk as mosquitoes don’t fly through the breeze it generates. Some scientists say a fan can also disperse the exhaled carbon dioxide, body odours and other sensory cues that allow mosquitoes to home in on people.
At the least, the fan’s an effective stopgap while I wait for more microbats, birds, dragonflies and native fish to do their thing.