Is Hamilton larviciding?
Yes, a larviciding program is underway. It consists of placing pellets or a briquette of a larvicide in storm water catch basins that are maintained by the City. This larvicide program is designed to reduce the mosquito population at the larval stage, and thus reduce the risk of humans contracting the virus. Larvaciding will be done where monitoring information shows that mosquito larvae are present. Plans do not include larviciding in standing water on private lands.
How does larviciding work?
Larviciding is the use of pesticides to control specific species of insects such as mosquito larvae. Larvicides are chemical and biological products registered for use in Canada by the Pest Management Regulatory Agency (PMRA), of Health Canada. Each product is approved for use to control specific types of insects such as mosquito larvae. Please note: Larvicide is in a pellet or briquette form and not sprayed into the air or onto surrounding land.
When will Hamilton begin to larvicide and where?
To be effective, larviciding must begin in the spring or early summer. Catch basins have been monitored this spring for mosquito larvae to determine when treatment should begin for the season.
Why larvicide in storm water catch basins?
Storm water catch basins are containers of water that can become breeding grounds of mosquitoes in many cities across North America. There are many types of mosquitoes. Those most likely to carry WNV breed in small, stagnant and even polluted pools of water such as those found in catch basins, rather than in places like open bodies of water like rivers or lakes. The use of methoprene is the most effective way to control mosquito larvae in catch basins.
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Source: City of Farmington |
How will I know if larvicides are being used in my area?
You will be given at least 48 hours notice in the newspaper and here on this website.
See the Notice of Application for Mosquito Control in the City of Hamilton.
If there is standing water on or near my property will someone come and apply a larvicide if I report it?
No. The City will not be applying larvicides on private lands. Keep in mind that rivers, creeks and lakes are generally not breeding grounds for mosquitoes (particularly the kind that spreads the disease to birds and humans) Treating small pools of water (natural or man-made) in urban or rural areas would be prohibitively expensive.
Rural residents, like all Hamilton residents, should focus on:
- reducing mosquito breeding sites around their homes,
- covering up with long sleeves and long pants made of light coloured, loose fitting, tightly woven clothing,
- repelling mosquitoes from uncovered skin by applying a mosquito repellent containing DEET when in mosquito prone areas. These activities are important to all residents of Hamilton.
What kind of larvicides are being used, and how do they work?
Two larvicides are being considered for use in Hamilton. Methoprene and Bti.
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Methoprene
Methoprene (a chemical larvicide) will be used in catch basins. It is a growth regulator that interrupts the mosquito life cycle and prevents immature mosquitoes from developing into biting adults. The mosquito larvae die before maturing. It is applied in pellet form, not sprayed into the air.
Methoprene is one of the simplest and most effective methods of reducing mosquitoes. It is licensed for mosquito control in Canada and the United States and can only be applied by licensed applicators. It is not available for consumer use.
For more information on Methoprene: Health Canada Fact Sheet - Methoprene (pdf)
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Bti
Bacillus thuringiensis israelensis (Bti) is a bacterium, which contains protein crystals that rupture digestive cells in mosquito larvae when ingested and is applied in granular form. It would be used to control mosquito larvae in temporary standing water. It is applied in granular form, not sprayed into the air.
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For more information on Bti: Health Canada Fact Sheet - Bti (pdf)
What is the impact of methoprene on humans and the natural environment?
Methoprene, when used as a larvicide for mosquito control in catch basins, is not harmful to humans.
Methoprene pellets dissolve slowly over a period of 3 weeks. Once dissolved, methoprene has a half-life of less than two days, which means half the concentration will disappear within two days, and the remaining half will be undetectable within ten days.
Methoprene breaks down quickly in water and in the presence of sunlight, and does not remain in the ground or leach into groundwater. Methoprene has low toxicity to fish and other aquatic organisms and poses little or no risk to other species when used in the amounts required to kill mosquito larvae. Application of methoprene in catch basins is not expected to reach rivers, ponds or Lake Ontario in an amount that would have a negative impact on the natural environment.
What is the impact of Bti on humans and the natural environment?
Bti has no acute or chronic effects on either humans or wildlife and aquatic organisms. It represents a very low risk to other non-target species and would only be used on temporary standing waters such as ditches and temporary ponded water sites.
What is the difference between "larviciding" and "adulticiding"? Is Hamilton planning to adulticide?
Larvicide can be applied in small targeted amounts to reduce the number of immature or larval mosquitoes before they develop into biting adult mosquitoes. Pellets of larvicide will be dropped manually into catch basins, not sprayed.
Adulticides are sprayed into the air to kill adult mosquitoes.
Adulticiding will be considered only if larviciding, together with other Integrated Pest Management strategies, are unsuccessful. Adulticiding will be considered as an emergency option for control.
What is the lifecycle of a mosquito?
Mosquitoes lay eggs in standing water. Mosquito development can take up to 14 days depending on factors such as water temperature, pH and food supply. In cooler temperatures, this life cycle could take up to a month.
Source: Leon County Mosquito Control
Even a saucer under a flower pot is enough to act as a breeding ground, so eliminate as much standing water around your property as possible. Unlike birds or other insects, mosquitoes do not fly very far from where they breed.
Can I use pesticide products on my property?
There are strict guidelines regarding pesticide use on private land. A great deal depends upon whether or not the water is solely on the private property or if the water drains into other water bodies. Guidelines will continue to be posted here.
Visit the Links and Resources page for a list of additional websites about West Nile virus and the use of pesticides.
What other efforts are being undertaken to reduce mosquito breeding sites?
Hamilton Public Health Services will be monitoring a number of pilot projects to control mosquito populations in and neighbouring health unit’s catch basins using alternative methods. These may include the flushing, steaming or vacuuming of catch basins and possible trials of mechanical devices using sound waves to kill larvae.
Have alternatives to pesticides been considered? (E.g. natural predators such as bats)?
Yes. Health Units in Ontario have researched and continue to evaluate natural predators and alternatives. Here are some highlights of this research.
Although bats, birds, and dragonflies among others eat mosquitoes they typically would not lead to control adult populations. Use of these predators alone is not effective.
- Bats
Bats are natural mosquito predators. However, research indicates that their primary food items are larger insects such as beetles or moths. It is not clear whether the urban environment provides enough other insects to sustain an enhanced population of bats. Enhancing the existing population of bats is of potential concern since bats can carry rabies.
- Purple Martins
There is a misconception that purple martins are useful for mosquito control. Martins and mosquitoes are not active at the same time or same location: martins are active during the day and feed high in the sky, while mosquitoes stay low in damp places during the day, or only come out at night.
- Dragonflies
Dragonflies do eat mosquitoes, however they also are active during the day whereas mosquitoes are most active at dusk and dawn. In addition, dragonflies are normally resident in larger ponds and creeks that do not support large populations of mosquitoes; therefore one cannot rely on natural dragonfly populations to control mosquitoes to any large extent. Dragonflies have been used in some areas for nuisance mosquito control. Review of the use of dragonflies for mosquito control indicates they do not result in controlling the spread of mosquito-borne disease.
- Mechanical devices (e.g. traps, zappers)
Mosquito magnets or mosquito traps emit CO2 or other chemicals which attracts mosquitoes. A fan or vacuum then sucks mosquitoes into the trap once they hone in on the device. They appear to collect a lot of mosquitoes, but no one has shown that they effectively reduce the number of mosquitoes or the number of bites in a backyard setting. Most claims that electronic devices control mosquitoes are not bona fide. For example, bug zappers kill a lot of insects, including beneficial ones, but are not particularly effective against mosquitoes alone.
What role does education play in the WNV program?
Public education remains an essential strategy in reducing the risk of exposure to WNV. Hamilton Public Health Services has developed a campaign to reach residents through a variety of means including existing City publications and on-line information, paid advertising and the circulation of materials in the community. This information will emphasize both what the City is doing and what residents, businesses and agencies can do. Messages focus on personal measures such as wearing protective clothing, using insect repellent, avoiding times and locations where mosquitoes are active and reducing stagnant water around the home. Strategies to reduce mosquito-breeding sites will be promoted to the private sector and with institutional partners such as school boards, hospitals, the university, and college etc.
Last updated: July 7, 2011