Mosquitoes on the rise in Winnipeg thanks to wet, rainy May

Winnipeg’s notorious bloodsuckers are on the rise thanks to a wet and rainy May, and some parts of the city are receiving more of their wrath than others.

“They have come out and are very active right now,” David Wade, an entomologist and superintendent of the insect control branch at the city, told CBC Up to Speed host Faith Fundal on Monday.

Wade said overall, city workers are finding more mosquitos in their latest surveys. That’s no surprise given the amount of rain Winnipeg had in May, which creates better, wetter conditions for mosquitoes to breed, he said.

The city’s insect control branch currently marks its Adulticiding Factor Analysis (AFA) level at “medium” as of Friday — an indicator of mosquito activity in Winnipeg based on several measures including trap count averages, rainfall and more.

In order to justify mosquito fogging several factors have to be met, including having an AFA level of “high,” and mosquito trap count averages of 25 or more for at least two consecutive days, said Wade. The citywide trap count average was 25 on Monday.

Another threshold that could trigger fogging is if a quarter of the city trap counts average 100 or more mosquitoes, he said.

But fogging is an approach to trying to curb mosquito populations once they’re already on the wing.

Most of the city mosquito management program is focused on measures like larviciding, which includes treating standing water in the city with a cocktail that kills larval-stage mosquitoes before they take flight, said Wade.

“We’ve been working very hard and if not for the mosquito larviciding program, the mosquito numbers would be a lot higher than they are right now,” he said. “We feel the program has been very effective.”

He said about 80-85 per cent of larvicide application in the city is done by helicopter. That has been complicated at times amid recent conditions with strong winds.

“It’s been unfortunate that we’ve had some windy days over the last couple of weeks, because when the winds pick up the helicopters can’t apply the insecticide…. it’s too risky with the amount of drift that can occur, so it does limit how often they can get out and fly.”

Trap counts are higher in some areas than others right now, like North Kildonan and Charleswood, where trap count averages were 110 and 72, respectively, as of Monday.

That isn’t necessarily abnormal though, said Wade.

For example, Charleswood has a lot of low lying areas and roadside ditches, and the area doesn’t drain as quickly as some other parts of the city, he said.

“Standing water persists longer, the soils stay saturated longer and it produces more mosquitoes as a result,” said Wade.

Wade said it’s soon to say how big of a nuisance the ankle biters could become further into summer, though the long-term forecasts predict a drier summer with periodic rainfall events.

Wade recommends homeowners do their part by trying to drain any standing water on their properties or otherwise treat those areas with insecticide.

He also encourages people with rain barrels to ensure those are covered, changing out bird bath water often, and to clear out eavestroughs to ensure water isn’t getting trapped.