Observer News

Abandoned Backyard Pools Pose Mosquito Risks

Temperatures are climbing rapidly in the southern Arizona desert. We had a lot of rain this winter and wildflowers are blooming, life is buzzing – spring is here!


A carpet of yellow flowers grows beneath Sonoran scrubs and cacti.
Spring in the Sonoran Desert. Image Credit: Molly McCormick, USGS RAMPS Program



Besides making outdoor activities possible, warmer temperatures reawaken a variety of insects…. including mosquitoes. Usually, we do not think of deserts as ideal mosquito habitats, but many mosquito species have evolved to persist during times of drought. In arid regions, mosquitoes are typically found near sources of water, such as oases or rivers, or in standing water in human-made structures. Pools or water storage tanks create an abundance of breeding habitats in urban areas, even in desert environments. While most of us are aware of backyard mosquito habitats such as buckets and old tires, we may not think of swimming pools as a potential health hazard.


Most residential swimming pools are properly maintained. Occasionally, however, pools can be abandoned during transitions between owners. There are over 10 million backyard pools in the United States, and it is estimated that 1% (10,000 pools) may be abandoned at any given time. Without a water pump in operation, it does not take long for the stagnant water to accumulate and attract mosquitoes. Even if a pool is drained while a house is being remodeled, it still can collect water after it rains. This is what happened in our neighborhood.


High resolution real-color satellite view of a suburban neighborhood with backyard pools.
See pool on lower left. This is an empty pool with water collecting in it. Image Credit: Screenshot captured from Google Maps.




Ground-level photograph of an otherwise empty backyard pool with a large puddle of rainwater collecting in the bottom.
Empty pool with water collecting in it. Image Credit: Carla McAuliffe





A man crouches next to the puddle of rainwater to collect a sample from the bottom of the pool.
Joe McAuliffe scooping a sample from the pool. Image Credit: Carla McAuliffe




This pool was next door and appeared to be a potential health hazard.We documented the habitat using the GLOBE Observer app’s Mosquito Habitat Mapper tool. We took photos and a video and tried to estimate the number of mosquito larvae present. There were literally thousands of larvae in the pool.



Mosquito larvae from the pool swimming around. Video Credit: Carla McAuliffe



Mitigation of standing water is an important action to protect communities from mosquito bites and the pathogens they carry. We reported the mosquito infestation to the Maricopa County Environmental Services Department. One mitigation strategy that they have used for years is biological control. They introduce mosquitofish, a non-native invasive species, to mosquito breeding sites that can’t be eliminated by dumping out water or covering the opening. The fish control mosquito populations by eating the larva. And in the past few years, the Arizona Department of Game and Fish began breeding and releasing an endangered, native mosquito-eating Gila Topminnow fish to control the mosquito population in the state. This turns out to be an effective way to save an endangered fish while also taking care of the mosquito menace.



A small fish with silver-yellow scales swims in clear water.
Gila Topminnow, an endangered fish used in local mosquito control. Arizona Department of Game and Fish.



Many communities are turning to Integrated Pest Management strategies as a scientifically based approach to reduce the numbers of mosquitoes. Biocontrol, such as the use of predatory fish, sensible application of insecticides, and citizen surveillance and mitigation are three actions that together support the reduction of mosquito populations locally. Citizen scientists armed with the GLOBE Observer Mosquito Habitat Mapper can support both surveillance and source reduction and play a key role in supporting healthy and nuisance-free communities.

Join the authors and Dr. Rusty Low to discuss this article on 21 May 2024 at 12:00 pm ET (16:00 UTC). Learn more and register at 


About the Authors:


Dr. Joe McAuliffe is an ecologist who studies plants and animals, including insects, in various environments around the world. He enjoys getting out in nature and whenever possible, catching fish.

Dr. Carla McAuliffe is a science educator who investigates learning and instruction in Earth and environmental science contexts. She loves the desert and the color turquoise.


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