If you felt that mosquitoes were particularly bothersome this summer and lingered longer than usual, it’s not just your imagination.
Several prairie cities experienced a surge in mosquito populations earlier this summer, leading some outlets in Manitoba, Saskatchewan, and Alberta to completely run out of bug spray due to the high demand.
Information gathered by the City of Edmonton indicated that the mosquito count in the city was 15 times greater in July than during the same month the previous year.
“While these numbers do not set any records for our area, they starkly differ from the past two summer seasons, which can amplify public perception,” commented Peter Daly, a biological sciences technologist at the City of Edmonton.
Saskatoon and Winnipeg also reported increased mosquito numbers in July compared to the previous year, based on data from those municipalities.
In southern Ontario, specialists suggest that the unprecedented rainfall that certain areas experienced this summer likely contributed to the surge in mosquitoes, explaining their continued presence causing itchy welts well into September.
Fiona Hunter, a professor of medical and veterinary entomology at Brock University, stated that southern Ontario has seen an increase in the Ochlerotatus trivittatus species this summer compared to prior years.
This species is recognized as a floodwater mosquito that deposits its eggs in low-lying, water-filled regions; the heavy rainfall in southern Ontario this year has created optimal breeding conditions for them, she explained.
“Consider all the rain we’ve had in southern Ontario this year. Saturated fields, low areas in lawns, roadside dips, and other poorly drained spots have repeatedly accumulated water,” she continued.
“This creates ample habitat for this particular mosquito, which likely accounts for the large numbers we are observing this year.”
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This species is notorious for being a relentless biter, she noted.
“I suspect that people are encountering this species more frequently this year, which may help explain why mosquitoes seem especially bothersome at the moment.”
The intense rain that struck the Greater Toronto Area and numerous other locales across southern and southwestern Ontario may have also triggered the hatching of many dormant mosquito eggs, according to Rosalind Murray, an assistant professor of biology at the University of Toronto.
“Consequently, we might observe a brief spike in population, particularly in areas that experienced significant flooding like Toronto,” she shared with CBC Radio’s Metro Morning.
Due to significant rainfall this summer, Ottawa continues to experience high mosquito counts, even as residents hope to move on from them. The CBC’s Jenna Legge reports.
Colder temperatures will reduce populations
However, once the region begins to experience cooler overnight temperatures, mosquitoes are expected to become less of a concern.
“They struggle in extremely hot conditions and can dehydrate. They also perish immediately when temperatures drop,” Murray explained.
“As we start to see significantly cooler nighttime temperatures, particularly below 10°C, we should witness a decrease in their numbers. Following the first frost, they will be gone entirely.”
This has already occurred in Alberta following a recent cold spell, according to Ken Fry, an entomology instructor at Olds College in Olds, Alberta.
Earlier this summer, Edmonton and Calgary faced a notably severe mosquito season, driven by substantial rainfall earlier in the year. However, he noted, mosquito populations have “essentially collapsed” due to the cooler temperatures observed in recent weeks.
Daly mentioned that Edmonton has already recorded a decline in the most prevalent local mosquito species, Aedes vexans, adding that since the city has experienced a warm fall so far, “we haven’t seen as drastic a decrease in their numbers as in some other years.”
Fry indicated that these insects could reemerge as temperatures are predicted to rise back to 20°C or higher over the next week in the area.
“Nevertheless, I don’t believe their populations will be anywhere close to what central Canada is currently experiencing.”