A decision to use mosquito larviciding or adulticiding follows a local risk assessment by your local medical officer of health in accordance with O. Reg. 199/03 under the Health Protection and Promotion Act.

In Canada, all pesticides are registered by Health Canada's Pest Management Regulatory Agency (PMRA). Once this agency has made a decision to register a pesticide product in Canada, the Ontario Ministry of the Environment is responsible for regulating its sale and use mainly through training, licensing and permit requirements.

Registered pesticides can be used at two different points in the life cycle of a mosquito : at the larva stage and at the adult stage.

In an effort to control mosquitoes in the larva stage, municipal larviciding programs will use pesticide products called larvicides. The larvicides will be placed in stagnant water, which is where mosquitoes prefer to lay their eggs (e.g., catch basin storm sewers).

There are a number of larvicides registered by the PMRA. However, only larvicides that have a minimal impact to the environment and do not present unacceptable risks to human health will be allowed for use by licensed applicators under an approved permit issued by the Ministry of the Environment. The public will receive advance notice before the community-based application of a larvicide. If you have concerns, you may wish to contact the local health unit to discuss your situation.

A permit is not required to larvicide on your own property if the water is wholly contained on your property with no outflow. A domestic larvicide product is now available to homeowners for limited use.

Control of adult mosquitoes involves the application of pesticides called adulticides in late evening when adult mosquitoes are most active and mosquito control is most effective. There are a number of pesticides to control adult mosquitoes registered by the PMRA.

For mosquito-borne disease control programs, Health Canada supports the use of malathion applied by ground or aerial equipment using ultra-low volume application equipment in urban areas.

Adulticides are applied by trained and licensed applicators. Advance notice must be given to the public before an adulticide is applied in a community.

The use of adulticides might be necessary among other activities when their use is indicated through the local risk assessment conducted by the medical officer of health in accordance with O.Reg. 199/03.

For more information, refer to the mosquito larviciding and adulticiding fact sheets available on the Ontario Ministry of the Environment's website.

They outline procedures that the public should know and follow in order to reduce potential exposure to pesticides. They also describe what pesticides are available to homeowners for domestic use.

May 2005

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