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After weeks of heavy rain created thousands of new breeding sites, soaring temperatures have accelerated mosquito development, leading to a sharp increase in populations across Regina, Saskatoon and other parts of the province.
“The weather has created the perfect storm,” said Ashley Thompson, manager of Parks Technical Services with the City of Regina.
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“We’ve had a lot more rain than we’re used to in June, and then the heat came, and it just accelerated the larval development.”
The increase in mosquito numbers has been dramatic.
Thompson said Regina’s monitoring program had caught about 780 mosquitoes during its first 11 weeks this season. Then, over just the last two days, city traps caught nearly 2,000 mosquitoes.
“It’s gone up quite a bit in the last two days,” she said.
Several mosquitoes cling to black clothing in Regina as hot weather following heavy rainfall causes mosquito numbers to surge. (Jacob Bamhour/980 CJME)
While mosquito numbers typically increase around the middle of summer, Thompson said this year’s spike is larger than what Regina has seen in recent years.
“We usually do see a spike around this week, next week, but it definitely is a bigger spike than we’ve seen.”
The culprit is a combination of abundant standing water and extreme heat.
Female mosquitoes lay their eggs in standing water. Once temperatures climb, larvae develop much faster, allowing new generations of mosquitoes to emerge in a matter of days.
Shawn Sherwood of Poulin’s Pest Control said Saskatchewan’s recent weather couldn’t have been much better for mosquitoes.
“Ten and a half inches of rain in three weeks, and then the temperature goes over 35 degrees,” Sherwood said. “This is mosquito nirvana.”
The same trend is playing out elsewhere in Saskatchewan.
The City of Saskatoon says mosquito activity is higher than it was at the same time last year, largely because increased rainfall followed by warm temperatures created ideal breeding conditions.
City entomologist Georgiana Antochi-Crihan said recent rainfall also reactivated dormant mosquito eggs that can remain viable for years.
“Recent drought conditions helped keep mosquito populations low by limiting breeding habitats,” Antochi-Crihan said in a statement.
“However, renewed rainfall has restored many standing-water areas that were previously dry, increasing the number of potential breeding sites throughout the region.”
Like Regina, Saskatoon has crews inspecting and treating standing water throughout parks, public spaces and other priority areas. However, the city says mosquitoes can still emerge between inspection and treatment cycles because warm temperatures speed up their development.
Regina’s mosquito control crews are also working five days a week, checking standing water throughout the city and treating breeding sites with VectoBac. This biological larvicide specifically targets mosquito larvae before they become adults.
“It does speed up the larval process, the development of the larva,” Thompson said. “So we have to act quicker. We have to get around to the water quicker and ensure that we’re treating it before they reach adulthood.”
Unlike some jurisdictions in the past, Regina does not spray to kill adult mosquitoes.
Thompson said adult mosquito control is expensive, requires specialized equipment and uses chemicals that are more toxic than products used to target larvae.
Instead, she says preventing mosquitoes from breeding is the most effective strategy.
Both Thompson and Sherwood are urging people to inspect their own properties for standing water.
“Make sure there’s no standing water in your yard,” Thompson said. “If you have rain barrels, cover them. Any tiny little bit of water can carry tons of mosquito larva, so make sure you’re emptying that.”
Sherwood echoed that advice.
“If it’s in a tire or if it’s in a bunch of plant pots that you’ve had sitting out, Mother Nature isn’t going to handle that,” he said.
“You’ve got to dump those things out. No breeding sites, no mosquitoes.”
Saskatoon is offering similar advice, reminding people to empty water from bird baths, pet dishes, eavestroughs, tarps, old tires and other containers. Water that can’t be removed should be covered, screened or treated to prevent mosquitoes from breeding.
“The city’s mosquito management program, combined with residents taking steps to eliminate standing water on their properties, remains the most effective approach to managing mosquito activity throughout the season,” Antochi-Crihan said.
Sherwood said products containing BTI, commonly sold as mosquito dunks, can also help by killing mosquito larvae before they become adults. One social media trend known as the “bucket of doom” uses standing water and BTI to attract egg-laying mosquitoes and kill their offspring.
“It will work, absolutely,” Sherwood said.
“The mosquito females will lay their eggs in there after they’ve had a blood meal. The larva will hatch out, and they’ll start feeding on the BTI.”
However, he cautioned that the method isn’t a cure-all.
“What you’re doing is you’re attracting mosquitoes to your yard to kill them. So there’s a little bit of a downside there.”
Sherwood also questioned the effectiveness of many backyard mosquito sprays.
“The main one that everybody is advertising right now is a garlic-based product,” he said. “It will repel some of the mosquitoes for a period of time, usually two or three hours. But the sunshine, the ultraviolet, breaks it down.”
He said mosquitoes from neighbouring properties quickly move back into treated areas.
Thompson also encouraged people to wear light-coloured clothing and use insect repellent when spending time outdoors.
She noted that the mosquito species capable of carrying West Nile virus typically begins to emerge around this time of year.
“So we will start seeing more of those,” Thompson said. “There is more of a risk that way, but we haven’t seen a ton of them yet.”
There is some relief in sight.
Thompson said standing water around Regina is beginning to dry up, and if hot, dry weather continues, the current mosquito boom should begin tapering off within the next week or two.
“It can be a lot worse,” she said. “But we definitely are seeing a higher spike than the last few years.”
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