Mosquitoes are present in San Diego, posing both a nuisance and public health concerns. Understanding local species and risks is important for effective prevention. San Diego’s unique climate contributes to mosquito activity, making awareness and proactive measures valuable.
Mosquito Species and Their Presence in San Diego
San Diego County is home to 28 recorded mosquito species, with 17 typically found each year. Nine of these species can transmit diseases to humans.
Two noteworthy groups are native Culex mosquitoes and invasive Aedes species. Culex mosquitoes, known as Southern House Mosquitoes, are primarily active during dusk and dawn. They are the main carriers of West Nile Virus (WNV), which has been detected in mosquitoes and dead birds in San Diego County. Local health officials monitor its presence.
Invasive Aedes mosquitoes, including Aedes aegypti (yellow fever mosquito) and Aedes albopictus (Asian tiger mosquito), are often called “ankle biters” due to their tendency to bite around the lower legs. Unlike Culex, these Aedes species are aggressive daytime biters and can bite multiple times. They are recognizable by their small size and distinctive black bodies with white stripes on their legs and backs. First detected in San Diego County in 2014, these invasive mosquitoes have since spread, adapting readily to urban environments.
Aedes mosquitoes can transmit diseases such as Zika, dengue, chikungunya, and yellow fever. While local transmission has historically been rare in San Diego, the potential exists due to these mosquito vectors. San Diego County reported its first locally acquired dengue case in 2025.
Aedes mosquitoes lay eggs in very small amounts of standing water, even a quarter-inch. Their eggs can survive for months in dry conditions before hatching when exposed to water. They breed both indoors and outdoors, often in residential containers. Aedes notoscriptus, another species identified in the county, can transmit dog heartworm.
Protecting Yourself and Your Property
Taking proactive steps minimizes mosquito exposure and reduces breeding sites around your home. Personal protection includes using EPA-registered insect repellents with active ingredients such as DEET, picaridin, oil of lemon eucalyptus, or IR3535. Applying these repellents to exposed skin and clothing deters bites. Wearing long-sleeved shirts and long pants, especially during dawn and dusk when Culex mosquitoes are most active, provides defense. Since invasive Aedes mosquitoes bite during the day, protective clothing is beneficial throughout daylight hours.
Property management plays a role in controlling mosquito populations. Since mosquitoes lay eggs in standing water, eliminating these sources is important. Residents should regularly empty water-holding containers weekly, such as plant saucers, buckets, birdbaths, and children’s toys. Clean and change water in birdbaths and pet dishes weekly.
Clogged rain gutters and old tires are common breeding grounds that should be addressed. For larger water sources like backyard ponds or unused swimming pools, mosquito fish can be introduced to consume larvae.
Ensure window and door screens are in good repair and free of holes to prevent mosquitoes from entering homes. If standing water cannot be eliminated, bacterial larvicides (liquid, dunk, or granule) can kill mosquito larvae and are safe for people, plants, and animals when used as directed. Report neglected swimming pools or areas with mosquito breeding to the San Diego County Vector Control Program. Reporting dead birds, especially crows, ravens, jays, hawks, or owls, to the Vector Control Program is important, as these can indicate West Nile Virus activity.