Author's note: We received two similar questions related to mosquito control, so they have both been posted here to avoid redundancy

Question #1:

Why does the spray you are using for mosquito control seem to kill bees and other insects but does not seem to reduce the mosquito population? And what are the known effects on humans? As I was walking over the footbridge, I started sweating profusely and was having breathing problems 30 minutes after the spraying was completed.

Question #2:

Tonight, prior to the mosquito fogging, there were an abundance of mayflies in my backyard and on the side of my house. Mayflies are an indication of clean air and clean water. Ten minutes after the fog truck passed through my alley, all of the mayflies laid dead on my patio. Why is it so important to contaminate our air with mosquito spray when there is such an obvious impact on other crucial species? I understand that mosquitoes are a nuisance, but there has to be a better alternative to this.


"The City of Laramie Mosquito Control program is an Integrated Mosquito Management program. It uses many different control strategies to control the nuisance mosquitoes that reduce our quality of life in the summertime, as well as reducing the risk of mosquito transmitted diseases. The city has established a West Nile Prevention Plan following the guidelines provided by the Centers for Disease Control (CDC).

Larval applications are made using environmentally friendly bacteria to a habitat that contains mosquito larvae to control these immature stages before they become flying, biting adults. These applications begin in mid-April and continue through September. Most of these applications occur in rural areas surrounding the city and go unnoticed by residents. Recent changes in the funding of the city program will allow a greater number number of these applications to be made on a greater number of acres in rural areas abutting the city. The goal of this increased larval control presence is to reduce the need for adult control applications. However, larval applications are costly and cannot control all mosquitoes within the flight range of our local species. Some can fly up to 20 miles. When larval applications cannot control the numbers of adult mosquitoes, we must rely on adult control applications to reduce the abundance. Adult control applications are utilized both in the city limits in the form of fogging trucks and in rural areas using aerial application techniques to limit the abundance and migration from the irrigated rural areas into the city.

Mayflies are often utilized to gauge the condition of water bodies, as they are found in bodies of clean water that have low pollutant levels cases. This fact, and the abundance of mayflies annually hatched from the Big Laramie River and other local tributaries such as Soldier Creek, Spring Creek, Harney Creek, 5 Mile Creek, and Sand Creek would argue against the contamination of air with mosquito control insecticides. Although the incident cited may have occurred in a time concurrent with a mosquito control application, it is unlikely that the treatment was actually involved. Mayflies are an extremely short lived adult phase of the insect lasting from a few hours to a few days. Mayflies will often hatch in unison and fly in mass to a location where they will complete the final molt from the sub-imago stage into the adult stage. The sub-imago period can last from 24-48 hours, again depending on species. The mayflies then molt into the imago, a sexually mature adult insect. The imago mayflies live from less than 90 minutes all the way up to 3 days, depending on species. Often, what is seen and perceived as dead insects is the molted skin from the sub-adult to the adult form, which is left clinging to buildings or strewn on surfaces.

Adult mosquito control operations utilize a procedure to apply insecticide at an ultra-low volume and use a special application nozzle that is designed to produce droplets that are sized to control insects that are mosquito size and smaller. The fogger applies the product at the rate of 3 ounces per acre. Of that 3 ounces, 4% of the fog is permethrin (insecticide), and another 4% is is pipronyl butoxide (a synergist that helps the insecticide perform reliably). The other 92% is a light pariffinatic oil that is used as a carrier. The nozzle uses a specially designed air blast vortex to shatter the product into tiny droplets that will remain suspended in the air long enough for mosquitoes to fly through the fog. Droplets are calibrated at between 10 and 30 microns (Droplet sizes are measured in microns. A micron is 1/1000 of a millimeter, or about 1/25,000 of an inch. In comparison, a human hair is about 100 microns in diameter). Fogging operations are conducted in twilight to dark hours to coordinate with the peak of mosquito host seeking and to reduce the likelihood of contact with pollinator species which do not fly nocturnally.

All insecticides utilized in the city program and all other programs nationwide are evaluated by the US Environmental Protection Agency (EPA). The EPA ensures that state and local mosquito control departments have access to effective mosquito control tools that they can use without posing unreasonable risk to human health and the environment. The EPA also encourages non-chemical mosquito prevention efforts, such as eliminating standing water that provides breeding sites. The agency educates the public through outreach efforts to encourage proper use of insect repellents and mosquitocides. Additionally, the EPA's rigorous pesticide review process is designed to ensure that registered mosquitocides used according to label directions and precautions can further reduce disease-carrying mosquito populations. The CDC, working closely with state and local health departments, monitors the potential sources and and outbreaks of mosquito-borne diseases and provides advice and consultation on prevention and control of these diseases. The CDC works with a network of experts in human and veterinary medicine, entomology, epidemiology, zoology, and ecology to obtain quick and accurate information on emerging trends which they develop into national strategies that reduce the risk of disease transmission. State and local government agencies play a critical role in protecting public health from mosquito-borne diseases. They serve on the front line, providing information through their outreach programs to the medical and environmental surveillance networks that first identify possible outbreaks. They also manage the mosquito control programs that carry out prevention, public education, and vector population management. 

The public's role in eliminating potential breeding habitats for mosquitoes--such as getting rid of any standing water around the home--is a critical step in reducing the risk of mosquito-borne disease transmissions. The public is also encouraged to make sure window screens and screen doors are in good repair. When venturing into areas with high mosquito populations, the public should wear personal protection such as long sleeve shirts and long pants, preferably treated with a repellent. People should use mosquito repellents when necessary, and always follow label instructions.

The city's Mosquito Control Division can be contacted by calling 307-721-5056."

Ask the City Of Laramie is your chance to send the city that burning question that you have always wondered about such as: “Why are there so many potholes on Grand Avenue?” or “Why did my water usage rates go through the roof?”

Please note that the City of Laramie will answer as many questions as possible at their discretion.