Why 2025 spring could bring a double dose of mosquitoes to the Fraser Valley

Consider stocking up on After Bite because the Fraser Valley could be headed for a particularly itchy 2025.

Record-low river levels in 2024 allowed locals to revel in a summer mostly free of blood-sucking mosquitoes. But a reckoning may be at hand, with a potential double dose of the pests possible in 2025.

Last winter’s warm, dry weather left BC’s mountains barren of snow and the Fraser River with a record-low spring freshet. The lack of water was bad for not only fish but also mosquitoes, whose low-lying breeding areas are “activated” by floodwaters.

Each year, Morrow Bioscience—the company hired to operate the Fraser Valley Regional District’s mosquito control program—monitors breeding areas in low-lying areas. When waters rise to a level at which eggs will hatch, Morrow applies a larvicide that can reduce the number of hatching bugs by around 90%. Despite those efforts, swarms of mosquitoes still survive to hatch and suck blood from residents.

(This is irritating for people but can be good for animals, like frogs and birds, that feed on mosquitoes. Mosquitoes also function as pollinators.)

In 2022, a winter of heavy snow caused the Fraser to rise well above its normal level. Morrow treated more than 3,000 hectares with larvicide. The work cost local taxpayers more than $400,000—a whopping $300,000 more than budgeted—but more than 100 people still contacted the FVRD’s mosquito hotline to complain about the pests. 

Last year, on the other hand, was  one of the quietest mosquito years in memory, thanks to the Fraser’s lack of water. Just 200 hectares of mosquito habitat—mostly on Stave Lake—required larvicide treatment last year. And the mosquito hotline was downright cold, fielding only two calls all year, neither of which complained about “notable mosquito annoyance,” according to a new report to the Fraser Valley Regional District’s board.

But the Fraser Valley’s residents may be about to pay for its itch-free year.

The expected arrival of La Niña this winter could bring increased snow to BC’s mountains. Although this year’s La Niña is expected to be relatively weak (if it arrives at all—meteorologists peg its likelihood at about 55%), it could still bring a higher-than-average freshet and more active mosquito breeding grounds. And there are likely to be a lot of mosquito eggs in those swamps.

In the FVRD’s report, staff warn that eggs that didn’t hatch because of last year’s low water still lurk in the region’s wetlands and may be triggered by this year’s freshet. The implication being that some areas could get two mosquito seasons in one. 

“These conditions will unfortunately mean more floodwater mosquitoes should be expected next year,” FVRD staff warn. Preparing for the mosquitoes will also come at a price, with morrow suggesting that next year’s budget “should consider a high-water year for 2025.”

One new piece of technology that Morrow had hoped to reduce dependence on helicopters won’t be available for the coming season because of provincial politics.

Drones

As The Current reported in 2023, Morrow has been hoping to use drones to apply larvicide in certain areas without many cottonwood trees. At the time, the company’s owner, Dirk Lewis, hoped to be able to fly the drones in 2024. That didn’t happen, although  the company then aimed to deploy the aircraft in 2025.

But although Morrow has obtained insurance and certification for Lewis to fly the drone, and found larvicides that can be deployed remotely, provincial rules continue to stand in the way.

Currently, only New Brunswick and Quebec allow drones to be used to apply pesticides. BC was working on its policies to allow drones to be used to eliminate bugs, but the work was paused in 2024, in part because of the provincial election, according to Morrow’s report to the FVRD. 

Morrow says it now doesn’t expect to be able to use a drone until 2026 at the earliest, despite “the financial and environmental savings this technology presents.”

So as early as February, helicopters and ground crews will begin visiting the region’s mosquito breeding grounds to try to stop the coming hatch before it starts. Meanwhile, FVRD staff and local residents will watch snowpacks to gauge just how much water may come down the Fraser—and how many mosquitoes may swarm come the spring and early summer.