Annual Mosquito Control Program

The City of Whitehorse administers an annual mosquito control program with a goal to reduce local mosquito populations and adult mosquito nuisance. All of the residential and industrial subdivisions extending from Hidden Valley in the north to Cowley Creek and Mary Lake in the south are included within the program’s service area. The annual program is administered by a very experienced environmental consulting firm, Duka Environmental Services Ltd., who have provided effective mosquito and biting fly surveillance and control programs for over 35 years.

The program involves public education, mosquito species surveillance, mapping, and control of larval mosquito development. Program operations are based on the principles of Integrated Pest Management (IPM) and the most environmentally sensitive methods of control are considered first. The annual control program does not spray for adult mosquitos and has not done so for over 20 years.

Mosquitos require standing water to develop and the most common habitats in the Whitehorse area are swamps, marshes, shallow ponds, non-flowing ditches and snowmelt in depressions, excavations/borrow pits, and tire ruts. Program efforts are focused on controlling mosquitos while they are in their larval stages, as opposed adult mosquito control, for several reasons.

  1. Larvae are concentrated in known locations (habitats), while adult mosquitos fly about and can disperse several kilometres.
  2. Larvae must remain in these waterbodies for 10 -21 days to complete their development, and, control applications are confined to these locations.
  3. Larvae can be effectively controlled, and overall mosquito populations suppressed by using physical, biological, and bio-rational (IPM) controls.

Mosquito surveillance and control program operations typically begin in late April or early May, depending on local conditions, and can extend through to October. Regular and frequent applications, completed from the ground and by air (helicopter), control developing larval populations, and are completed throughout the season, where, and as required. Both private and publicly-owned properties are included in the annual program.

The larval control product of choice is a naturally occurring soil borne bacteria called Bacillus thuringiensis var. israelensis or by its common name VectoBac 200G. This bacterium is heat-killed, and as such it is not alive and does reproduce or accumulate in the environment. It works through the attachment of enzymes to the stomach cells of mosquitos, black flies, and some biting midge larvae, causing these cells to burst, and the larvae to die. It has no effect on other organisms including fish, wildlife, birds, mammals, amphibians, reptiles, and other insects.

It is important that residents understand that mosquitos are a natural part of the environment. Although the biological control agent used is extremely effective in reducing mosquito numbers, no amount of mosquito larvicide application will totally eradicate mosquito annoyance in all areas. The vast amount of habitat located outside the boundaries of the treatment program is such that in certain areas some level of adult mosquito annoyance should be reasonably anticipated.

The goal of the program is to reduce adult mosquito nuisance for residents and visitors. It will not eliminate mosquito populations. Residents and business owners can contribute to their program by eliminating standing waters by filling and grading of depressions, ensuring snowmelt waters drain and evaporate and that window screens are in place. Residents who have ponds, marshes and swamps located on their properties, and which are too large, or desirable to be drained, can participate in the program and have these sites surveyed and treated, as appropriate.