Mosquito Population

July 10, 2019

The Buzz on Mosquitoes- be prepared.

The recent heavy rain and warm temperatures result in perfect conditions for a boom in the mosquito population. Until recently, we were fortunate with very low activity; however, with the recent rains, vast areas provincially are now experiencing spikes in numbers. In Estevan we are currently enduring low numbers of two nuisance species of this pest (Aedes vexans and Ades dorsalis). Although we have control measures for the larvae around the City, these species can fly up to 20 km in favorable conditions. There is an estimated 268,000 square kilometres of potential mosquito habitat in Saskatchewan, it is not possible to eliminate them all. If you venture into the country ecosystems, you will experience the wrath of mosquitoes in extreme numbers. In the City we have significantly reduced the numbers, but we cannot eliminate them entirely. Larvicide is the most efficient strategy and the City remains committed to this technique due to its effectiveness, the low cost of application, and the environmental friendliness of the product. Fogging is not a viable option and most Cities have moved away from that option. The only time Estevan will fog is under the direction of the Ministry of Health and this would be in response to a health-related matter (e.g. West Nile outbreak). Fogging is very expensive and lasts, at times only four to six hours before new mosquitoes move in to take over the vacated habitat. We are in mosquito country, take precautions, wear repellent, try to avoid the dawn and dusk high activity times, wear light colored, loose clothing , screen the windows and diligently eliminate any water sources on your property as they are major sources of breeding grounds which are outside the scope of the City’s larvicide program. For more information see the bulletin below.

Mosquito Control Bulletin Although there are over 40 known species of mosquitoes in Saskatchewan, we experience only a few of them here in Estevan. The common species emerging in the early spring are the nuisance mosquitoes (Aedes. Sp.), which are normally followed in July by the more commonly known Culex genus. The Culex tarsalis species is the insect vector known to carry West Nile disease. Control and monitoring techniques are increased during the time this species is known to inhabit in the area. The life cycles of each species differ in timing of emergence and behavior. Even with the best of programs, we will still see ebbs and flows as different species or new generations emerge throughout the season with weather patterns. A proper municipal monitoring program is critical for a successful control program. The City’s approach to mosquito control consists of three phases: 1. Public information campaigns describing the City program and providing advice for property owners in controlling mosquito populations 2. Monitoring and controlling larval populations 3.Monitoring adult populations in partnership with the Ministry of health.

Public information campaigns. Through social media such as this bulletin, information is shared with the public. A critical factor in the life cycle of any mosquito is the requirement of standing or stagnant water exceeding seven days. One cup of standing water can produce hundreds of mosquitoes and there are sources of standing water everywhere including ditch lines, sloughs, wetlands, irrigated areas and storm drains to name a few. This year, the City has implemented properly timed irrigation in our green spaces to better control
the possibility of standing water, additionally; we are reviewing green space areas for depressions that are holding water and we are levelling the grounds to eliminate the habitat. There are many areas here with this issue; we are focusing on the parks this year and moving into other green spaces in future years on an ongoing basis. Equally important to this habitat are the smaller, yet high producing sources commonly found in back yards of homes and businesses. Take an inventory of your property and drain any sources of standing water where possible. Common sources include tires, containers, tree wells, bird baths, depressions in yards, tarps covering items, etc. Drain or eliminate the sources of habitat. If you irrigate, take notice if standing water remains, level the ground with soil and seed to avoid ponding. Larvae Monitoring and Control The City monitors all potential habitats within three kilometers of the City limits. As we build the program, we will expand this boundary looking for high producing areas. A twenty-five square kilometer area was reviewed with a known entomology expert to determine where potential problem areas exist. This aspect of the program is very important as it allows the City to reduce unnecessary treatments and focus on known problem areas through data analysis. The priority areas for treatments are habitats containing larvae where there is a high incidence of human outdoor activity including but not limited to: sports venues, school zones, cemetery, public buildings, parks and trails. Secondary to this are the breeding grounds outside of frequently used areas for example edges of wetlands in the south west area of the City. At each site, a minimum of 10, 350ml samples are taken and if the average of these samples exceeds 4 larvae, the City will treat with biological products such as Vectobac or Vextolex. These registered pesticides are naturally occurring bacteria (Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus respectively), used for many years and they do not cause harm to other animals. Records of the treatments are kept for reference and to assist with provincial monitoring. Adult Monitoring In addition to larval monitoring, the City works with the Ministry of Health in surveying the adult mosquito populations. Live traps are set in specific areas within the City where mosquitoes are active. Each week, the samples are collected and sent to labs for identification and testing for diseases. The correlation of data between larval and adult numbers provides an indication of the effectiveness of the larval reduction program and whether changes to our program are necessary. For more information, please contact the Parks Division at (306) 634-1880

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