The human factor | Ecological fight against mosquitoes: myth or reality?

With a simple high-pitched “zzz,” they can ruin any summer evening. But is there an effective and environmentally friendly way to combat mosquitoes?

“We see all sorts of products in stores against mosquitoes. How do you find your way around them?” asks Véronique.

Mosquitoes are formidable predators: over the course of evolution, they have developed a whole range of tools to track us. “They use their sense of smell, their sight, the heat we give off, the CO₂ “That we exhale,” says Ben Matthews, a professor in the zoology department at the University of British Columbia. “And their taste, when they happen to land on us.”

Result: even if we manage to disrupt one of these mechanisms, “there are redundancies which mean that they can still manage to sting us,” the researcher emphasizes.

Despite everything, there are solutions to fight against them, on different scales. But not all of them are effective or good for the planet.

The famous DEET

On an individual level, the most common solution is to spray yourself with a product containing DEET – a synthetic substance that forms a film on the surface of the skin and repels mosquitoes.

In Canada, only products containing 30% or less DEET are approved, and it is recommended not to exceed 10% for children. They are considered safe “when applied according to label directions,” according to the Health Canada website.

“It’s an effective product, but it degrades very slowly,” says Jacques Brodeur, director of the Plant Biology Research Institute at the University of Montreal. “We’re starting to realize that our water sources, our lakes, our rivers contain detectable quantities. It’s not a problem right now, but it’s accumulating in the environment. What will the situation be like in 10 or 15 years? It’s hard to say.”

Alternatives to DEET

There are also insect repellents based on icaridin (or picaridin). A study published in 2018 showed that a product containing 20% ​​of it was highly toxic to salamander larvae – a predator of mosquito larvae. However, further studies would be necessary to better assess the risks of this insect repellent for the environment.

“It’s also tempting to go natural, but you have to apply a lot of it very frequently, and it doesn’t work as well as DEET,” Matthews notes. Products with lemon eucalyptus essential oil, for example, typically only offer two hours of protection (compared to six hours for those with 30 percent DEET).

Many other devices exist on the market: Thermacell-type mosquito repellents, ultrasound-based devices, incense spirals, bracelets, etc. They have no known negative effects on the environment, but their effectiveness has not been scientifically proven when used alone, the Institut national de santé publique du Québec states on its website.

“Green” solutions?

The “green” solutions recommended by experts are often physical rather than chemical – the idea is to create a barrier to prevent the insect from biting us.

For example, they recommend wearing covering, loose-fitting clothing with thick fabric to avoid being bitten through it, using a mosquito net or a fan powerful enough to prevent insects from landing on the skin. Of course, all these solutions have their limits; in particular, it is still recommended to use insect repellent when traveling in an area where mosquitoes are likely to transmit a disease.

Empty planters, buckets, tarps, rainwater collection basins, wheelbarrows, unused outdoor swimming pools, old tires, kayaks… If you have a yard or balcony, “you can also try to remove any source of stagnant water to prevent mosquitoes from laying eggs there,” explains Julia Mlynarek, an entomologist at the Montreal Insectarium.

“But there is no real miracle solution,” emphasizes Jacques Brodeur. “The best thing is to combine several approaches, so that it is effective.”

Read “Help, Mosquitoes Love Me!”

And on a large scale?

About 130 municipalities in Quebec go so far as to spread Bti in their bodies of water when their residents are too bothered by biting insects. However, scientists are concerned about the impact of this biological larvicide on biodiversity.

Read “Be careful, it’s going to sting!”

Other cities have traps installed on their territory. There are different types: some attract insects by emitting light and CO₂others are electric traps. For example, pilot projects were carried out in Châteauguay, Gatineau and Saint-André-de-Kamouraska with such traps. The three municipalities managed to capture approximately 1 million mosquitoes each in one summer. In Gatineau, however, nearly 20% of the insects captured were not mosquitoes.

On a larger scale, research is underway to genetically manipulate mosquitoes, to make them more vulnerable to an insecticide, for example. In some areas, by releasing millions of sterile (non-biting) male mosquitoes, it has been possible to wipe out entire populations of these insects.

But these large-scale solutions are not unanimous. For the experts interviewed by The Pressthey should remain exceptions and be used only in regions where mosquitoes are vectors of disease. In Canada, they are responsible for the transmission of the West Nile virus, but cases remain rare: there have been 47 cases in the entire territory for the year 2022.

“We have to remember that mosquitoes are still a vital part of the food chain, and they’re also pollinators,” Matthews said. “You always have to be extremely careful about removing a species from an ecosystem.”

Read “Pests: Scientists concerned about genetic modifications”

Green light: CopenPay

Picking up rubbish, taking public transport, walking or cycling: for almost a month, Copenhagen will be offering rewards to visitors and residents who take action to help the environment.

The initiative, called “CopenPay,” involves “transforming green actions into ‘currency’ for cultural experiences,” explains a press release from the city’s tourism office. The rewards? A vegetarian meal, a kayak or boat ride, museum entry or an electric bike ride. The initiative could be made permanent if its results are conclusive.

Source: Agence France-Presse

He said

For some industries, this reuse of water will allow savings of 15% to 80% in drinking water.

Marc Fesneau, French Minister of Agriculture and Food Sovereignty. On July 9, the French government published two texts relaxing regulations to allow food industries to recycle their wastewater. Manufacturers of yogurt, sausages and frozen vegetables, in particular, were eagerly awaiting this measure: they use large quantities of water to wash their ingredients and their facilities.

37 ºC

A simple and effective way to cool artificial grass would be to store rainwater under the lawn and cool it by capillary action. An idea that has proven itself: a team of Dutch researchers conducted the experiment in Amsterdam, during a heatwave in 2020, and showed that the surface temperature of a pitch covered with conventional artificial grass reached 62.5 °C, compared to 37 °C for this cooled artificial grass – and 35.3 ºC for natural grass.

The researchers hope to reduce heat islands in cities. However, installation costs could be up to twice as high as those of traditional artificial turf.

Source: Frontiers, July 8, 2024

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