Mosquito Season Has Arrived

June 17, 2021

Mosquito season has arrived in the Fraser Valley, and some residents, particularly those within proximity of the Fraser River, may begin to experience their annoyance. To reduce the number of these floodwater mosquitoes, the FVRD's annual nuisance mosquito control program is underway. 

Crews with Morrow BioScience Ltd. have been monitoring water levels since early May and have been aggressively treating all known mosquito breeding sites as larvae appear. This includes foreshore areas within the region as well as throughout the Fraser River Islands. Treatments and monitoring will continue through the summer, as is needed. 

How does mosquito control work?

Morrow BioScience Ltd. provides mosquito control services throughout the region and has been conducting mosquito control for over 20 years within the Lower Mainland. Residents may notice mosquito control contractors in brightly coloured vests sampling the flood and seepage waters for mosquito larvae, the life stage targeted during mosquito control operations.

“We are doing our very best to reduce floodwater mosquitoes so that they remain at tolerable levels and allow residents to be able to enjoy outdoor activities,” said Dirk Lewis, Lead Biologist.

Bacterial larvicide has been applied by ground since mid-May and helicopter treatments will occur along the Fraser River foreshore and Fraser River islands during the month of June. Aerial and ground treatments may continue through the summer, as dictated by environmental conditions necessary for floodwater mosquito development. The larvicide applied is not toxic to people, wildlife, or pets. 

Within the Lower Mainland, mosquito eggs laid in previous years along the banks and seepage sites of the Fraser River are beginning to hatch. Floodwater mosquitoes are triggered to hatch in the presence of water, typically from the freshet, when the weather starts warming up and snowmelt increases the Fraser River levels. 

Once the mosquito eggs have hatched and the larvae have started to develop, mosquito control contractors apply a bacterial larvicide to the seepage water to kill the larvae. The larvicide is made up of toxins from bacterial spores that target mosquitoes. When the mosquito eats the bacteria, it dies quickly. Mosquito development sites within the region will be monitored once or twice weekly through early August or as needed depending on water levels.

Learn more about this program

What can residents do to reduce mosquitos?

Residents can do their part in reducing mosquito breeding sites around their properties by removing or refreshing standing water daily. These areas include birdbaths, old tires, clogged gutters, animal troughs, and kiddy pools, to name a few.   

Residents can reduce their exposure to mosquito bites by wearing long-sleeved shirts and pants, choosing light-coloured clothing, using insect repellent, deploying mosquito netting at home, and ensuring window screens are properly installed and maintained.   

For updates follow Morrow BioScience Ltd. on Facebook.

To report possible mosquito breeding sites, please call our Mosquito Hotline at 1-888-733-2333 or email