Mosquito Adult
Susan Ellis
Mosquito Larvae
About Mosquitoes
What are the common and important mosquitoes in Saskatoon?
There are 19 different mosquito species found in Saskatoon. When we monitor, control and discuss mosquitoes, we often use two terms “nuisance” and “vector” to describe mosquitoes. Vector mosquitoes are those that are responsible for the transmission of diseases such as West Nile virus; whereas, nuisance mosquitoes do not transmit disease and are only bothersome because of their bite. The nuisance mosquitoes are active in the spring and early summer and are very noticeable because of their large numbers. The vector mosquitoes are most common in the mid to late summer. In the Prairies, Culex tarsalis is the most important vector mosquito as it is capable of transmitting the West Nile virus to people. This mosquito is not easily noticed as it appears late in the season and has a very subtle bite. The behaviour and seasonality of C. tarsalis means that people are often unaware of this mosquito and do not protect themselves from being bitten.
Why are there so many mosquitoes in Saskatoon?
Weather patterns make mosquito populations hard to predict but warm weather and rain are ideal conditions for mosquitoes. With the vast amount of standing water in and around Saskatoon, the mosquito population may be more prevalent this season.
What is the Mosquito Life Cycle?
Eggs: Depending on the species of mosquito, eggs are either laid singly or in floating rafts on the water surface. The most common mosquitoes in Saskatoon are in the genus Aedes (Ochlerotatus) which typically lay eggs in muddy areas or temporary pools of water. Female mosquitoes of the genera Anopheles, Culiseta, Coquellittidia, and Culex lay floating egg rafts on the surface of open bodies of water. The eggs can remain un-hatched waiting for rain or a flooding event for several years.
Larvae: The eggs hatch into larvae, the immature stage of the mosquito life cycle. This life stage is aquatic and can be found in many standing bodies of water. Larvae are commonly referred to as wrigglers because of the way they twist in the water. This wriggling allows larvae to reach the surface to breath and move to the bottom to feed on algae and other small organisms. Any container that holds water for several days can be suitable for mosquito developments. These habitats can include rain barrels, tires or bird baths to name a few. Elimination of these sites will greatly reduce the number of adult mosquitoes.
Pupae: Larvae turn into pupae after growing through four larval stages. As pupae, they are beginning to metamorphose into adults and no feeding occurs. The pupa will move to the surface of the water and the soft skin will split when the adult is ready to emerge. Pupae are also known as tumblers because of the movement they make in the water.
Adults: Adults are the most identifiable stage with their slender body and legs and an all too familiar buzz as they fly. Only females bite as they need the protein and iron from blood to develop their eggs. When females bite they inject saliva that contains chemicals that promote blood flow. Mosquito borne diseases are often transmitted as mosquitoes inject their saliva. Males do not bite and feed primarily on nectar.
Mosquito Control in Saskatoon
What is the City doing to control mosquito population in Saskatoon?
The City’s mosquito control program focuses on efforts to control the aquatic life stage of the mosquito (larvae). We regularly monitor mosquito development sites (small bodies of water) within approximately 945 square kilometres including the City of Saskatoon and a surrounding buffer. The City also monitors the adult mosquito population using New Jersey light traps and Centre for Disease Control light traps. We do this to ensure our control measures are effective and to track the presence of West Nile virus in adult mosquitoes.
How does the City monitor mosquito larvae?
The City’s pest management staff is trained in larval identification. To determine if a body of water requires treatment, the staff will sample using a standard dipper to determine if larvae are present. When there are at least two larvae per dip an area is treated. This can mean the entire water body or just areas where the larvae were found.
How are larvae treated?
Larval mosquitoes are killed using a biological larvacide called Bacillus thuringiensis var israelensis (Bti or Vectobac®).
How is it applied? Is it dangerous?
The bio-larvacide is a type of bacteria that is applied to the surface of the water using a backpack sprayer. The species of bacteria only affects filter feeding insects, with the greatest impact on mosquitoes and black flies.
Does the City tell residents when larvacides are used?
After treatment a sign is posted to indicate that a pesticide product was used at that location. The sign includes the product that was used, the product registration number and the date of application. The signs indicate to both the pest management staff and the public that an area has been treated. We also issue letters requesting access to privately owned land in the RM of Corman Park. Last year we mailed out 1300 letters down from 2200 letters the previous year. We have received permission from 1600 landowners and this continues to increase every year.
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How residents can help control mosquitoes
Residents should remove standing water from property and clean eaves troughs regularly. Ensure items in and around your property like pool covers, saucers under flower pots, children’s toys, pet bowls and wading pools are regularly emptied or replaced with clean water.
Empty and clean bird baths often and cover rain barrel openings with mosquito screening. Also, clear your yard of debris that could hold water. Cutting long grass reduces resting sites for mosquitoes and is another way that residents can help control mosquitoes.
How to Prevent Mosquito Bites
Here are some tips to prevent mosquito bites:
- Wear light-coloured, long-sleeved shirts and long pants.
- Use mosquito nets over play pens, strollers and carriages for infants.
- Apply insect repellent with DEET. Do not use DEET on children under six months of age.
- Keep time spent outdoors to a minimum between dusk and dawn when Culex tarsalis are most active.
- Ensure all windows and doors in your home are tight-fitting and properly screened.
About West Nile Virus
Will the risk of West Nile virus be higher this year due to all the standing water in and around Saskatoon?
It is difficult to predict the risk of West Nile virus this season. West Nile virus was present in very low levels in 2010. The first positive pool of West Nile virus was detected in Estevan Saskatchewan in early August. In total, there were nine positive pools from Saskatchewan and zero in Saskatoon. This was unusual in that the numbers of Culex tarsalis were very high, but there was very little West Nile virus activity. One of the possible explanations was the lower temperatures throughout the Culex tarsalis season.
While mosquito larva control will provide protection by reducing mosquito numbers, it will not eliminate the risk of West Nile virus. Health Canada recommends the use of repellents containing DEET.
About DEET
- DEET concentrations should not exceed 30% for adults and 10% for children two to 12 years of age.
- For infants six months to two years old, no more than one application of 10% DEET is recommended.
- DEET should not be used on infants less than six months old.
- Some lower concentration DEET products can provide protection for a period of time. These products are recommended for people who suffer allergic reactions to products containing DEET, or who have irritated, sunburned, bruised or broken skin, and skin conditions such as cancer, dermatitis, acne, eczema or psoriasis.