Mosquito Control

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Frequently asked questions

How many treatments have been done in 2021?

In May, two aerial applications and 47 ground applications at 35 sites were completed. In June, multiple treatments were applied to several ponds and marshes in Porter Creek, Hidden Valley, Granger, Whistle Bend, Crestview, Mt. Sima, McCrae and Mary Lake.

Duka continues to sample and treat larval development where it is found, and conduct inspections and sample sites every eight to ten days.

What is the area of treatment?

Treatment occurs within and adjacent to Whitehorse, from Hidden Valley to Cowley Creek, which covers 600 hectares.

Is the scope of treatment the same as previous years?

The current scope is sufficient for an average, to slightly above average season of mosquito development. Aerial applications focus on and include swamps, marshes and snowmelt-filled areas located within 0.5 to 1 km from residential, commercial and built up areas.

The scope may need to be increased in future years to account for an expansion of residential areas.

Why does it seem like there are more mosquitos this year? 

Whitehorse’s snowpack accumulations were over 291% of normal on May 1, 2021, and with cooler temperatures during the first few weeks of May, the onset of snowmelt was delayed. As a result, the amount of snowmelt and standing water outside of town and in undetected forested areas in town would have been greatly increased over that of an average year. These populations are the likely cause of reported annoyance this year.

The warm weather of late also makes adult mosquitos, and other nuisance insects, such as black flies and no-see-ums increasingly active. This increased activity makes them more annoying, aggressive and visible.

2021 Mosquito Population Management and Reduction Program

Larval surveying and monitoring for the annual mosquito control program began in late April. The goal of the program is to reduce adult mosquito annoyance for residents and visitors. It will not eliminate mosquito populations, and residents should expect to observe some adult mosquitos.

The majority of larval mosquito development locally occurs with accumulation of snowmelt runoff and precipitation in depressions and established ponds. Permanent mosquito habitats can include stagnant seepage and spring-filled ponds, marshes, non-flowing ditches, depressions and any other natural or man-made container that can hold water.  

Focus of the Control Program

Experience has proven that the best way to achieve relief from adult mosquito annoyance is through effective control of larval mosquito populations. The annual control program does not spray for adult mosquitos and has not done so for over 20 years.

Control program efforts are focused on the identification and treatment of mosquito larvae using the biological larvicide VectoBac 200G, which contains the bacterium, Bacillus thuringiensis var. isrealensis (Bti). This bacterium is specific in its control of mosquitoes and does not affect other insects, fish, birds or mammals (including humans), livestock and pets. It does not harm beneficial mosquito predators like wasps, dragon flies, birds and bats.

All larvicide applications are directed to infested mosquito development habitats located within, and adjacent to, the City of Whitehorse, extending from Hidden Valley to the Cowley and Wolf Creek areas using aerial (helicopter) and ground-based, hand-broadcast methods. To date the control program has treated over 600 hectares of habitat by air and from the ground. The program focuses on larval development habitat located within with 5,000 to 1,000 m (1km) of residential, commercial, recreational and industrial developments, and for most of the past 20 seasons this has been a sufficient level of effort and scope.

Every now and then, unique or exceptional weather or floodwater conditions can create conditions, and larval habitat, beyond the reach of program operations. The 2021 summer season is one of those years.

Program field biologists continue to monitor and treat mosquitos in identified development sites. Adult mosquito light trapping equipment has been deployed to collect mosquito samples from areas reporting annoyance.

Mosquito Populations this year

A late season melt, of above average (291% of normal) snowfall accumulations, resulted in widespread flooding and subsequent larval mosquito development. Larval development occurring outside of program treatment boundaries has produced increased adult mosquito populations. Over the past few weeks, these have migrated, either passively (by wind) or actively (by flight), into areas of public use and habitation.

The warm dry weather conditions of late has increased their activity and made them more aggressive and noticeable to residents. The fortunate aspect of the increased temperatures is that it also increases adult mosquito mortality by causing them to desiccate and dry out.

Residents can help

While the larval mosquito control program will help reduce overall mosquito populations, residents and visitors should still be prepared to protect themselves from adult mosquitos. Ensure window screens are in good condition, and wear loose, light coloured clothing. Avoid perfumed skin care products and shampoos, and consider using repellents and controls such as mosquito coils or mosquito magnetsTM.

Residents can help reduce the likelihood of mosquito bites by eliminating mosquito development sources around their property, and by using personal protection methods. Regular draining and refilling of wading pools, livestock watering troughs, bird baths and emptying of covered boats, canoes or wheelbarrows reduces a source of mosquito development.

To report a possible development site (stagnant ditch, pond, swamp), residents are encouraged to leave a message for the program technician at 867-633-BITE (2383) or directly with Duka offices through 1-604-881-4565 or email, Office and field staff will follow up with telephone contact and on-site inspections as necessary.