'Anticipate seeing more': Edmonton mosquito population could double under new plan

After grounding pesticide spraying from helicopters, city officials say Edmonton's new mosquito control strategy could take several years to reach peak effectiveness.

On Monday, city council voted to take a more natural approach to mosquito management by ending the aerial program and instead emphasizing biological pest control measures and education campaigns. The ground and ditch spraying of larvacide will continue this season.

At a media availability on Friday, the city explained what the new pest management strategy would look like for the upcoming mosquito season.

Mike Jenkins, integrated pest management coordinator, said that mosquito numbers would increase with the aerial program's loss, especially after it rains or snows when spraying would typically occur.

"Certainly, within the areas that used to be covered by the aerial program, we are going to see the development of larvae and mosquitoes emerging from those," Jenkins said.

"We do anticipate seeing more of those mosquitoes entering the city," he said. "How much exactly? We are not entirely certain."

According to Jenkins, the city's pest control approach with the aerial component had an effectiveness ratio of 5:1, with around five times as many mosquitoes outside of the city as inside.

He expects that ratio to decrease now to around 2.5 or three times, meaning a potential doubling of mosquitoes.

Since 1974, the City of Edmonton has had a mosquito control program, including an aerial component. Jenkins said the last time the city had a summer without helicopter mosquito management was in June 2020, when supply chain issues prevented the procurement of enough pesticides.

"During that period we did see that we still had a significant impact on the mosquito population," he said.

"We were effective in reducing them," he added, "due to the actions of the ground and ditch program."

BIOLOGICAL PEST CONTROL COULD TAKE YEARS

When it comes to implementing natural pest control, Jenkins said it could take several years for them to reach peak effectiveness.

The city will be developing and naturalizing habitats surrounding stormwater facilities to encourage more dragonflies to develop, create a bat roosting site pilot program, and enhance biodiversity surveillance and monitoring to see what "other biological control options" could be developed to naturally reduce mosquito populations.

Jenkins said the bat box trial will see the installation of up to 50 homes in locations around the city, which will then be monitored for activity levels and fungal testing.

"These operational enhancements in addition to the existing ground ditch and surveillance programs will increase our understanding of the efficacy of alternative techniques for mosquito control and allow us to make informed decisions for program modifications in the future," Jenkins said.

"There will almost certainly be some delay. Any natural control methods, bat boxes, things along those lines, could take quite some time, could be several years for them to develop to the level that we are hoping to get them to."

More mosquitoes are expected in the next few years, Jenkins said, but "hopefully long-term" the population numbers will be able to be "reduced significantly" as biological pest control measures come online.

"Several of these species have fairly long generation times," he added. "There's no guarantee bats will even move into bat boxes."

EDUCATION AND PUBLIC AWARENESS

The city will also educate Edmontonians about actions that can be taken to reduce hatching sites for mosquitoes on individual properties.

Those recommendations include clearing up standing water, covering rain barrels so mosquitoes cannot lay eggs in them, regularly replenishing and replacing the water in birdbaths, or running oscillating fans on patios to disturb the airflow deter mosquitoes.

According to Jenkins, those measures are more effective than other commercially available pest control measures.

When asked if the city is worried property owners will turn to spraying pesticides themselves or hiring contractors to do so, director of infrastructure operations Phil Herritt said the city will focus on building awareness about more natural alternatives.

"At this point, we think with a good communications plan in place we are going to be able to help people come to a more natural control method without reverting to a lot of those pesticides," Herritt said.