Mosquitoes will stay active for next 3 weeks thanks to intermittent rain, according to expert

The blood-sucking pests are out in full force, and they're not going away any time soon, thanks to ideal breeding conditions.

Entomologist says conditions ideal right now for mosquito breeding

An unusual amount of rain in a short period of time has provided a boost to the mosquito population in Calgary.   1:58

This year has already been worse for mosquitoes than the past three years, and according to entomologist John Swann from the University of Calgary, it's not going to improve any time soon.

"I look at the long-term weather forecast and it's, you know, I wouldn't say it's Armageddon but … it is good conditions now for breeding mosquitoes," Swann told the Calgary Eyeopener on Wednesday.

"It has been so damp, and it's continued to stay damp. We're getting rain every three or four days now."

Swann says a rainy spring got it all started.

And now this week, the large bodies of standing water, along with continued intermittent rain days, are providing a perfect hatching ground for mosquitoes.

"One of the worst species is a temporary breeding one," Swann said. "One of the most common ones in the summer, which does breed in the temporary [standing water] is called aedes vexans, and it's probably across the country and it's maybe 80 per cent of our mosquitoes that we see in summer."

There are about 45 species of mosquitoes in the province, and we see about 20 of them in Calgary.

"Those ones that we were seeing in May … they almost looked like little wee Cessna planes, they're so darn big," Swann said. "And these ones that are nailing you right now are these insidious little things that pop out of the long grass and they're everywhere and relatively small."

Swann says the city does a good job of controlling the mosquito outbreaks.

"The city always monitors," he said. "They're always very cognizant of what's going on out there. Quite frankly, as an entomologist, I'm impressed by the control levels that they go to. And it's quite safe control."

University of Calgary entomologist John Swann recommends moving your lawn to reduce mosquito habitat, and wearing long sleeves, lighter colours and a safe repellent to avoid bites. (CBC Calgary)

Swann says the female mosquitoes do all the biting, because they need "a blood meal" for their eggs. 

And you are not imaging it, mosquitoes can sniff us out.

"One of the first things they cue in on, believe it or not, from 50 metres away they can detect the carbon dioxide you're giving off in your breath," Swann said.

He notes that exercising "just increases the CO2 you're giving off."

Mosquitoes also show a preference for blood type.

"The chemical compounds you give off in things like your sweat help them," Swann said. "They prefer type O … over Type A. Type B blood falls somewhere in between. But there's a very distinct difference between Type O and Type A for getting bitten."

You can't control your blood type, but you can protect yourself by avoiding early morning and late evening outings. If you must go out, Swann suggests wearing lighter-coloured clothing and long sleeves. He also recommends either a DEET-based repellent or a less-common repellent called icaridin.

"It's a derivative of pepper plants," he said. "Just as effective."

You can also control your home landscaping.

"Keep your grass cut shorter," Swann said. "Because they're looking to get down in the heat of the day into the long grass. And the same with clearing out around your shrubs. Keep that relatively clear. It's less of a reservoir for them to sit in, in the heat of the day."

As for how long this current "high season" will last, Swann says the weather forecast tells the tale.

"Well, I can see two weeks out and it still looks pretty rainy," he said. "So I would say for at least the next three weeks you're going to have lots of mosquitoes out there."

With files from the Calgary Eyeopener.

With files from James Young


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