Determining and Eliminating the Source of a Mosquito Nuisance

The Allegheny County Health Department works diligently to keep residents safe from vector-borne diseases. This video shows you what we do to test mosquitoes in our area:

Backyards are a major source for mosquito nuisances in Allegheny County. Anything that can hold stagnant water for more than 5 days provides a place for mosquitoes to lay their eggs and for their larvae to grow. Mosquitoes need as little as a half-inch of water to complete their life cycle. Biting adult mosquitoes are less than a half-inch in length and should not be confused with other flying insects that hang around backyards such as midges and crane flies.

If stagnant water cannot be eliminated, unused pools and water features must be treated on a regular basis with a mosquito pesticide (larvicide). Areas like clogged rain gutters may not be as obvious as a swimming pool, but it is your responsibility to survey all areas of your yard to make sure that mosquitoes are not breeding. Use the Mosquito Breeding Site Checklist(PDF, 127KB) for potential mosquito breeding sites to begin looking.

To determine and eliminate the source of a mosquito nuisance, the Health Department must have help from the residents who are affected. We cannot survey every neighborhood for all the things that hold water and breed mosquitoes. On the other hand, an informed resident can take a walk through their area and identify conditions that may be contributing to the problem.

It is a violation of Article VI(PDF, 523KB) of the County Health Code to have water-holding containers, improperly maintained swimming pools, landscape ponds, and scrap automobile tires stored on properties. If these things are present in your neighborhood, a complaint can be submitted by calling the Housing and Community Environment Program at 412-350-4046 or by filling out our online complaint form.

Once you file a complaint, the health department will send the responsible party a Pre-Inspection Notice (PIN). The notice alerts them to the problem and requires them to fix the offending conditions and come into compliance with the County Health Code. We allow a period of time for people to comply before an inspector will come out to check it out. If the condition that was reported is still present upon inspection, the stagnant water will be treated by a vector control specialist if possible, and a Notice of Violation (NOV) will be sent to the responsible party. If the property fails a second inspection, the responsible party will receive a warning letter that may result in a required appearance in Magistrate’s court and/or fines.

If you received a notice from the health department about an unused swimming pool or water feature on your property, see an explanation on how to best comply: Complying with Health Department Notice About Unused Swimming Pools and Water Features(PDF, 346KB).

If you want to file a complaint about mosquitoes but are not willing or able to identify a property with possible causative conditions, call the Housing and Community Environment Program at 412-350-4046 to further discuss the problem. If a likely breeding site property cannot be determined, we will then ask a public official in your municipality and/or a vector control specialist to visit the property and help resolve the problem.

What is ACHD doing about mosquitoes and the diseases they carry?

Wetlands throughout Allegheny County that are known to be breeding sites for mosquitoes are treated by the health department every spring to help knock down the mosquito population in those areas before the summer, and mosquito season, begins. Excellent, EPA-approved methods and materials are applied to the wetlands to prevent a large number of nuisance mosquitoes from hatching and traveling into nearby neighborhoods. Residents who live near a wetland may report a mosquito nuisance to the health department by calling the Housing and Community Environment Program at 412-350-4046.

Allegheny County Health Department is also part of a large statewide surveillance and control program actively involved in trapping mosquitoes to track the spread of West Nile virus and other viruses that infect people and animals. Every summer since 2002, West Nile virus has been detected in certain species of mosquitoes (Culex pipiens and restuans) in Allegheny County. In City of Pittsburgh neighborhoods with West Nile activity, thousands of catch basins holding stagnant water are treated with pesticide every summer by health department staff in an effort to curb a major urban source of Culex breeding. Up-to-date mosquito surveillance data and information about mosquito spray events can be found at

County neighborhoods with high levels of West Nile virus activity based on surveillance data may also be treated with a truck-mounted sprayer to knockdown infectious mosquitoes. Up-to-date mosquito surveillance data and information about mosquito control events can be found at The health department puts out press releases when this spraying is occurring.

Can stagnant water be treated for mosquitoes?

If possible, eliminate all sources of stagnant water on your property. The next best option is to treat the water where mosquitoes breed with a larvicide (see Larvicides for Mosquito Control from the Environmental Protection Agency(PDF, 36KB)), which are available from hardware stores and online retailers. The most commonly used residential product is a biological pesticide made from a naturally occurring soil bacteria called Bacillus thuringiensis, also known as Bt or Bti. These products (e.g. Mosquito Dunks, Mosquito Bits, etc.) will kill mosquito larvae and are not harmful to other aquatic plants/animals, people, pets or wildlife. Bt products do not persist in the environment (meaning that they breakdown quickly and are no longer effective after a short period of time) and must be reapplied monthly, as directed on the label.

Another effective mosquito larvicide applied to water is made from a synthetic insect hormone called Methoprene (e.g. Mosquito Torpedo, etc.). These products do not kill mosquito larvae quickly but rather stop the life cycle of the mosquito so that it never becomes a flying, biting adult. One advantage to Methoprene is that mosquito larvae stay in the food chain longer for other animals to eat. Like Bt, methoprene is safe and effective at controlling mosquitoes without having harmful effects on mammals, birds, fish or other aquatic insects. When using pesticides, always read and follow the label.

What is the Asian Tiger mosquito and is it here in Allegheny County?

The Asian Tiger mosquito or Aedes albopictus (see: Tame the Asian Tiger Mosquito(PDF, 5MB) Brochure from PA Department of Environmental Protection) is an invasive, day-biting mosquito that has been found and remains in parts of Allegheny County since 2010. This mosquito is native to Southeast Asia and first came to the United States in 1985 in shipments of used tires. Since then, the species has spread throughout parts of the U.S. It does well breeding in artificial containers, scrap automobile tires, and small, hidden sources of stagnant water, which is part of why it is so important to find and eliminate as many of those sources as possible.

The Asian Tiger is a particularly aggressive mosquito that likes to bite people all day long rather than just at dusk and dawn like Culex mosquitoes that transmit West Nile virus. It is also a potential transmitter of Zika, Dengue, Chikungunya, and Yellow Fever, although fortunately none of these viruses are currently found in the mosquito population in Allegheny County. It can also transmit Dog Heartworm, which is a parasitic roundworm that affects dogs. The best way to control the Asian Tiger mosquito is to consistently eliminate and/or treat stagnant water in your backyard.

If you have any questions about this information please call the Housing and Community Environment Program at 412-350-4046.

It is always the pesticide applicator's responsibility, by law, to read and follow all label directions for any pesticide being used. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author and the Allegheny County Health Department assume no liability resulting from the use of these recommendations.

Other Mosquito Resources