Posted at 5:00 a.m.
Are there more mosquitoes this year? Due to the spring weather, the mosquito eggs all hatched at the same time. They are therefore present to spoil our barbecues. But beware, the worst could be yet to come!
A cold, then warm spring
For André-Philippe Drapeau Picard, entomological information officer at the Montreal Insectarium, there is no doubt: the weather conditions favored the reproduction of biting insects. “We had a relatively cool spring and the heat came all of a sudden in the middle of May. The mosquitoes were probably dormant and they all came out at the same time during the heat wave. The scientist stresses, however, that there are no precise data on mosquito populations in Quebec, “but one can think that their emergence was concentrated in time”.
After the heat… the rain
Samuel Genest, general manager of Abat Extermination, also speaks of an “incredible boom” in births during the heat wave. The problem is that the heat wave in May was followed by heavy rainfall. When the baby mosquitoes reached their adult stage after three weeks, they definitely found moist places to lay new eggs. Some species lay 50 to 300 of them. “If we have a context of heat in the corner of Saint-Jean-Baptiste, all these eggs will hatch and we risk ending up with another boom,” says Mr. Genest.
Worse in some regions?
It’s not a myth! There are more mosquitoes in certain regions of Quebec such as the Laurentians and the North Shore than in the Eastern Townships, for example. “It’s linked to the habitat available,” explains Mr. Drapeau Picard of the Insectarium. “In southern Quebec, there used to be a lot of wetlands, but these have been largely drained for agriculture. So there are fewer habitats for mosquito breeding. Conversely, there are many wetlands such as lakes, bogs, marshes and swamps further north of Montreal.
Useful or harmful?
They bite us, it itches and swells! Could we do without these unwanted insects that spoil our late summer evenings? Not really, replies Mr. Genest! “Within the food chain, mosquitoes serve as food for many species such as birds and bats,” he explains. At the larval stage, they are also eaten by batrachians and fish. Mosquitoes also act as pollinators.
Mosquito-borne diseases
Mosquitoes in Quebec do not transmit malaria, dengue or Zika. They can, however, carry the West Nile virus. In 2021, 14 people contracted the virus, including five in Montreal, according to the Ministry of Health and Social Services. The majority of sufferers do not develop symptoms, although some individuals experience fever, headache, myalgia and sometimes rash. The West Nile virus has been present in Quebec since 2002.
Spreading insecticides in cities?
In 2021, 42 municipalities received authorization to spray their territory with BTI to control mosquito populations. It was not possible to obtain figures from the Ministry of the Environment and the Fight against Climate Change for 2022. Some scientists are concerned, however, about the use of this insecticide on biodiversity, since mosquitoes and their larvae serve as food for other species. “What we know from certain studies that have been done in Europe is that BTI also has impacts on insects other than black flies and mosquitoes,” says François Labelle, an agricultural producer at the head of of a citizens’ committee that opposed the use of BTI in Labelle. The municipality of Laurentides has decided to end the use of this insecticide this year.