Mosquito control relies heavily on understanding the biology of the species involved, knowledge of its habitats, and constant monitoring of the control area. Our most successful method for reducing pest populations is to attack the immature stages of the pest's life cycle when they are most vulnerable.
In other provinces where disease carrying mosquitoes are a problem, adult control is justified but is relatively inefficient. In the Edmonton area, where mosquitoes are primarily nuisance only, adult control is minimal.
Since 1974 the City's mosquito control program, developed by the University of Alberta, has targeted larval stages of nuisance Aedes spencerii species. In general, our larval control programs drastically reduce the production of Aedes mosquitoes within the City's 1,400 square kilometre mosquito control boundaries.
Comprehensive monitoring programs throughout this zone identify treatment needs which vary with the impact of snowmelt and summer rainstorms. The amount of rainfall can result in anything from no action at all to a full blown aerial and ground-based larviciding operation.
Instant mosquitoes - just add water
For speed and efficiency, over 90% of treatment is contracted to helicopter services that use dry, granular larvicide formulations. Off-road sites that are inaccessible to helicopters and ditch habitats along road allowances are treated by the City's ground-based wet spray delivery equipment. Applications are restricted by:
- Mosquito development beyond the fourth larval instar since these are no longer susceptible to the treatments available
- Windy or rainy conditions
- Approximately 5% of the outer area accessible by helicopter is not treatable because of owner refusal, noise sensitive farming operations, beehives or other environmental concerns
These restrictions can result in advanced stages of mosquito development prior to the completion of a campaign. In addition to these normal types of restrictions, high water levels in the spring can also result in greater problems as moving water cannot be treated. Larvicides are applied only to temporary or semi-permanent bodies of water containing larvae.
Permanent bodies of water are not treated because they contribute very little towards nuisance mosquito production. Additionally, these habitats support more complex insect communities including mosquito predators like dragonflies.
Treatment campaigns are terminated with the development of pupal stages of the mosquito which can appear in as little as a week to ten days after hatching. Information about spraying activities and adult mosquito populations is publicized through media releases and interviews.
Edmonton’s mosquito control program utilizes a larvicide product containing Bti, a selective fly gut toxin derived from bacteria (Bacillus thuringiensis israelensis). Summertime post-treatment surveys show that application of Bti reliably manages most populations of larval mosquitoes. Bti has been used by Edmonton’s mosquito control program since 1980 and continues to be used in most situations.
Products containing Bti, however, are much less effective in treating snowmelt during Edmonton’s cool spring conditions. In these situations, the control program utilizes a conventional insecticide containing chlorpyrifos (Facts about chlorpyrifos). Post-treatment surveys show that applications with this product effectively terminate the majority of larval mosquito development under all known habitat conditions.
Key dates in Edmonton's battle against mosquitoes:
- 1953 - Aerial mosquito control initiated.
- 1972 - Spraying DDT for mosquitoes was discontinued.
- 1973 - Mosquito control monitoring laboratory started.
- 1975 - Edmonton's district operated mosquito program was centralized under a single pest control unit.
- 1980 - Introduction of bacterial control product (Bti) for usage in sensitive areas.
- 1991 - Initiated mosquito development site reduction (landfill) program.
- 1993 - Discontinued mosquito adulticide program (fogging) targeting the city's river valley and ravine system.
- 1993 - Provincial funding assistance eliminated (approximately 50% of budget); eventually all surrounding municipalities discontinued mosquito control in the capital region.
- 1993 - Implemented global positioning technology to assist helicopter pilots in identifying "no fly" areas such as noise-sensitive farming operations.
- 1994 - Implemented a cost-saving efficiency with a one-person ditch crew versus two-person.
- 2003 - West Nile virus found in Alberta. The province initiated a three-year funding program for mosquito vector detection and source reduction.
- 2012 - Implemented mobile devices in the field to map standing water and collect larval mosquito development and population data in real-time.