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City of Calgary beats down on summer mosquito population boom

Mosquitoes are feasting on Calgarians in higher numbers than usual this summer thanks to a perfect storm of factors contributing to their exaggerated increase.

This week alone, City of Calgary Pest Management has caught 7,000 mosquitoes in traps.

“We’ve actually caught more [this month] than we did in the last two years combined,” said Alexandra Pepperdine, a City of Calgary integrated pest management technician. 

Last year, 13,000 mosquitos were caught from July to August and only 4,000 in 2020.

“We tend to notice it more in the east part of the city,” said Pepperdine.

“The edge of the city tends to get the worst just because there’s lots of habitat there.” 

Calgary houses more than 20 species of mosquitoes. And they aren’t afraid to put in the leg – or wing work – to find hosts.

Pepperdine said they’ll travel up to 10 kilometres to find a meal.

“They can be widespread everywhere even if there isn’t necessarily a habitat nearby,” she said. 

Causes for Mosquito Increase

The city takes a proactive approach to controlling the summertime nuisance. It does this by applying a bacterial product, Bacillus thuringiensis, into water where mosquito larvae are likely to be.

The larvae feed on the bacterium which becomes pH activated and breaks down the lining of their digestive system. The larvae then stop feeding and die. 

In the spring, depending on the moisture, the city performs an application of pesticide in the middle or end of May. It is most effective in warmer temperatures and if “there’s younger larvae in the water” because they feed actively.

“Ideally, we also do it after there’s any sort of large rainfall,” said Pepperdine.

The weather conditions play a large factor due to wind and rain that prevent the team from aerial pesticide application.

Due to the sensitivity of the bacteria, which “breaks down differently” under various conditions, it tends to disintegrate after two to three days.

Citizens under attack

Calgarians are noticing the high-flying skeeter numbers as well.

“There are definitely more mosquitoes this year than usual. I have a lot of mosquito bites all over me too,” said McKenzie Towne resident Caroline Paulino.

“There are more in the forest, especially near the (Bow River).”

Pepperdine correlates the recent heavy rainfall with the mosquito increase.

“We have had a lot of floodwaters lately. The mosquitoes will often lay their eggs in soil or physically wet areas that commonly flood over. Those eggs can ferment for several years, so they’re just waiting for rain to come,” she said.

With a wet summer for the past month and a half, it created the perfect breeding ground for mosquitoes.

“More wet areas create a lot of egg hatches that have been laying dormant in the soil for a few years. It’s kind of creating the perfect situation, and then you get some warm weather. Then those eggs can hatch quite rapidly.”