Fewer floodwater mosquitoes hatched in the Fraser Valley in 2024 due to lower river levels, but a new report posits 2025 could be a different story. 

Morrow Bioscience, the Fraser Valley Regional District mosquito control contractor, presented the board with a report in December reviewing the 2024 floodwater mosquito control season. 

According to the report, the 2024 snowpack was below the historical average, leading to a lower-than-average freshet from May to early July.

鈥淭he Lower Fraser River levels never exceeded 5 meters in 2024, therefore, the necessary environmental cues needed for the hatching of floodwater mosquitoes at some associated sites were never received. Lower Fraser River levels did not trigger a compounded number of floodwater mosquito eggs to hatch since peak river levels were far below those of 2023,鈥� the report reads. 

The floodwater mosquitoes emerge from eggs laid in wet soil near riverbanks during the previous year. As waters rise, the eggs hatch into larvae which the FVRD monitors and treats using a bacterial larvicide. 

鈥淭he goal of the program each year is to reduce the number of larvae available so that the population of adult mosquitoes that eventually merge is kept at tolerable levels,鈥� the report reads. 

Just 200 hectares of floodwater mosquito habitat needed treatment in 2024, compared to 3,000 hectares in 2022.  Most areas only required ground treatments for mosquitoes last year, with the Stave Lake area emerging as the exception. 

According to the report, Stave Lake water levels reached a four-year high in 2024. 

鈥淪tave Lake was the only area that required aerial treatments this year, as this system is independent from the Fraser River system (being a controlled reservoir)," the report stated. 

Three aerial campaigns were required at Stave Lake floodwater mosquito habitats on June  5, 11 and July 5. 

Morrow Bioscience also provided information on what the 2025 season could look like.  The report anticipates more floodwater mosquitoes than in recent seasons.

According to the report, a La Nina weather pattern is predicted for 2025, which can mean relatively high snow levels and a wet spring. 

鈥淧eak river levels are expected to exceed those seen this year. Not only will this likely result in more mosquito-breeding habitat to become active, the mosquito eggs laid previously that did not  hatch in 2024 will be available for hatch in 2025,鈥� the report reads.