Larviciding
What is larviciding?
Where do we larvicide?
How many standing water sites are there?
When do we larvicide?
What larvicides do we use?
How does larviciding for nuisance mosquito control differ from vector control?
What is larviciding?
The City of Winnipeg Insect Control Strategy calls for an aggressive larviciding program as it is the most effective and environmentally acceptable method of mosquito population reduction. The largest component of the Insect Control Branch’s mosquito control program is the larviciding operation. Mosquito larvae are not mobile and concentrated in water sites which make them the most vulnerable stage of the mosquito lifecycle. By targeting larvae in ditches, pools and containers, countless numbers of mosquitoes are destroyed before they reach the flying adult, biting stage.
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Where do we larvicide?
Larviciding of all known larval development sites within the City of Winnipeg , on public and private property, and up to 10 km beyond the City limits is carried out on a regular basis. Larviciding is conducted by both ground and helicopter crews. If you would like to find out if your property is already an existing listing or if you would like to to have your property assessed for standing water and larval development, please contact 311. Mosquito larvae occur in many types of aquatic habitats. The most common nuisance species lay their eggs in temporary or ephemeral rainwater pools of 1 to 2 weeks duration. Vector species generally lay eggs in all types of containers, semi-permanent and permanent aquatic habitats.
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How many standing water sites are there?
The number and size of sites varies throughout the season and from year to year based on a number of factors including rainfall, ground saturation, temperatures, commercial/residential development and alterations to land drainage.
We monitor and treat up to approximately 33,000 hectares of water area on an ongoing basis. Our Global Information System (GIS) database contains approximately 7,000 listings, many of which contain multiple sites.
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When do we larvicide?
Larviciding operations are carried out more-or-less continuously from late-April through September every year. Often, larviciding crews must work 7 days per week, especially when excessive rainfall causes the widespread hatching of mosquito eggs in floodwater larval development sites.
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What larvicides do we use?
The City of Winnipeg’s Nuisance Mosquito Control Program uses a combination of biologicals and chemicals which are applied according to Health Canada’s Pest Management Regulatory Agency (PMRA) regulations.
The City of Winnipeg uses the following biological larvicides: Bacillus thuringiensis var. israelensis, known as Bti under the trade names Vectobac® 200G, Vectobac® 1200L; and Bacillus sphaericus under the trade name Vectolex® CG.
Biologicals are utilized for all larviciding in environmentally sensitive areas such as residential areas, playgrounds, parks, bee hives, etc. and in temporary water bodies that are not connected with natural water bodies.
The City of Winnipeg uses the following chemical larvicides: Methoprene under the trade name Altosid®; and Chlorpyrifos under the trade names Dursban® Turf or Dursban® 2.5G. Chemical larvicides are used in sites that typically have no direct contact with the public. All applications meet or exceed provincial permit requirements.
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How does larviciding for nuisance mosquito control differ from vector control?
Targeted larviciding occurs in areas where ‘primary vectors’ are developing in water bodies. A vector species is a mosquito which can possibly transmit a variety of diseases. The primary vector mosquito species in Manitoba are Culex tarsalis and Culex restuans. Vector control is required when the primary vectors begin to emerge as early as mid-June in Winnipeg. These targeted sites undergo larviciding and monitoring more often as the reduction of vectors is far more important from a public health protection perspective than the control of nuisance species. The Insect Control Branch conducts larviciding for vector control on a municipal/provincial cost-shared basis as a component of the Manitoba West Nile Virus Program.
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