City launches annual mosquito control offensive

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This article was published 03/05/2023 (1057 days ago), so information in it may no longer be current.

For many Winnipeggers, the long-awaited arrival of sunny and warm spring weather has signalled the inevitable return of one of their biggest foes: mosquitoes.

There was good news on that front Wednesday, when the city launched its annual mosquito control program and offered a prediction on what to expect in the short-term.

“Our spring population should be low, and our spring and early summer is looking favourable,” said David Wade, superintendent of insect control. “Beyond that, I can’t predict with certainty.”

Wade said the city can only look two weeks in advance with certainty because Winnipeg’s weather is “quite unpredictable.”

Frequent and heavy rainfall, which results in standing water, can lead to more of the blood-sucking pests.

“We have drier conditions now than a year ago, so we’re starting off good,” Wade told reporters at the insect control heliport on Tyne Avenue in East Elmwood.

The city’s biorational (environmentally friendly) larviciding program is underway while spring mosquitoes hatch in standing water in ditches and low-lying areas.

The mosquito control program is starting at its normal time of year, said Wade.

Below average winter precipitation and a slow spring melt have produced favourable conditions for the city, which is using ground crews and four helicopters to curb the mosquito population.

Until mid-September, crews will be monitoring and treating more than 69,000 acres of water area, based on weather conditions.

They are using two types of larvicides which target larvae in the aquatic stage to prevent them from becoming adults.

“They’re out in the water now, and we’re going around… those sites using the most environmentally-friendly way of targeting the mosquito population,” said Wade.

The city uses Bti, or Bacillus thuringiensis israelensis, which is a bacteria that only targets mosquito larvae. It also uses methoprene, a juvenile growth regulator.

Fogging for adult mosquitoes will only take place as a last resort, when certain conditions are met, according to the city.

The adulticiding factor analysis (a type of mosquito risk assessment) must be high, the city-wide average trap count must be at least 25 female mosquitoes for two consecutive nights, and at least one quadrant must be in the range of 100 female adult mosquitoes.

The city uses the insecticide DeltaGard 20EW.

Residents who don’t want their property to be fogged can apply for a 90-metre buffer zone.

Winnipeg’s mosquito traps are being switched on Thursday. The first counts will be posted on the city’s website Monday.

This year’s budget for mosquito control is almost $10 million.

Property owners can also play a part in helping to reduce the city’s mosquito population. Wade encouraged people to dump or drain any standing water in their yards throughout mosquito season.

The city also suggests residents cover containers that collect rain water, fill low-lying areas to prevent standing water, and use biological larvicide.

With the 2023 season underway, Wade’s fingers are crossed for weather conditions that work in the city’s favour.

An ideal situation would be comparable to 2021, when heavy downpours were minimal, he said.

“Our main nuisance species, aedes vexans, requires those summer rainfall events,” said Wade. “We can handle some rain, just not a lot of heavy rains.”

Monitoring of West Nile virus, which is spread to humans through the bite of an infected mosquito, usually begins around May long weekend, said Wade. The surveillance program lasts into September.

Mosquitoes aren’t the only insects the city will be keeping an eye on during the warmer months.

Tree pest caterpillar surveillance started this week. Wade said caterpillars haven’t hatched yet, so crews are monitoring egg masses.

A control program usually starts around May long weekend.

The city’s programs for emerald ash borers and elm bark beetles typically begin in June and around the end of August, respectively.

chris.kitching@freepress.mb.ca

Twitter: @chriskitching