Mosquitoes that bite during the day in Orange County are almost always invasive Aedes mosquitoes, either Aedes aegypti (the yellow fever mosquito) or Aedes albopictus (the Asian tiger mosquito). Unlike the native mosquitoes most of us grew up with, which bite mainly at dusk and at night, these species are active during daylight hours and breed in tiny amounts of water close to homes. The solution is less about spraying and more about finding the small containers in your own yard where they breed.
How Invasive Aedes Arrived in Orange County
The Orange County Mosquito and Vector Control District first collected invasive Aedes in Mission Viejo in 2015. Later that same year, residents in Garden Grove called the district about aggressive mosquitoes biting their legs during the day, and the district confirmed the invasive species there. By 2018, the district had documented infestations in more than 20 cities across the county, including Anaheim, Costa Mesa, Garden Grove, Huntington Beach, Irvine, Orange, Santa Ana and Tustin.
These mosquitoes spread mostly by hitchhiking. Their eggs can survive dry for months on the inside walls of containers, so a plant pot, tire or bucket moved from one place to another can carry them to a new neighborhood. Once established, they are very hard to eliminate from an area.
How to Tell Invasive Aedes From Native Mosquitoes
Invasive Aedes are small, dark, and marked with bright white stripes or bands on their legs and body. Native Culex mosquitoes, the main West Nile virus carriers in California, are usually brown and plain by comparison.
Here is a quick comparison:
When they bite: Aedes bite throughout the day and into the evening. Culex mostly bite from dusk through the night.
Where they bite: Aedes tend to go after ankles, lower legs and the backs of arms, often approaching from behind. Culex bite wherever skin is exposed.
How they behave: Aedes are persistent and will follow you around the yard. Culex are more likely to be noticed buzzing around at night indoors.
Where they breed: Aedes use small containers, sometimes as little as a bottle cap of water. Culex prefer larger standing water such as catch basins, storm drains and neglected pools.
If you are getting bitten at lunch on the patio, while gardening in the afternoon, or while sitting in the shade on a weekend morning, Aedes are the likely culprit.
Why They Bite During the Day
Aedes aegypti evolved to live closely alongside people. It prefers human blood, rests in shaded spots close to homes, and is active when people are outside, which is during the day. Aedes albopictus is similarly a daytime biter. Both species do much of their biting in the morning and late afternoon, but in shaded yards they will bite at almost any hour.
This behavior is why traditional evening fogging or bug zappers do little against them. They are resting in your shrubs during the times those tools run, and they are attracted to people rather than light.
Where They Breed in Orange County Yards
Because invasive Aedes need so little water, the sources are usually close to where you are being bitten, often in your own yard or the yard next door. The most common breeding spots we find in Orange County include:
Plant saucers, potted plants and planters without drainage holes.
Buckets, watering cans, toys and pet water bowls left outside.
Clogged gutters and the low spot at the end of a downspout.
Birdbaths and fountains that are topped off but not scrubbed.
Rain barrels without tight lids or fine mesh screens.
Tarps, pool covers, tires and anything stored outdoors that collects a little water.
Air conditioner condensate lines dripping into a low spot.
Bromeliads and other plants that hold water where leaves meet.
Why Emptying Water Is Not Enough
Invasive Aedes lay their eggs on the inside walls of containers, just above the waterline. When the container dries out, the eggs survive and wait. The next time the container fills, from rain, a sprinkler or hand watering, they hatch. That means simply tipping out a bucket does not get rid of the eggs. Containers need to be scrubbed with a brush, turned upside down, thrown away, or covered.
A weekly routine works best: walk your yard once a week, tip and scrub anything holding water, and store buckets and pots upside down or under cover.
Health Risks
Invasive Aedes can transmit viruses such as dengue, Zika and chikungunya in parts of the world where those viruses circulate. In Orange County, these viruses are not regularly transmitted locally, but health officials watch for cases because a traveler infected abroad could be bitten by a local Aedes mosquito and start local spread. These mosquitoes can also transmit dog heartworm. For most residents, the main issue is the constant itchy bites that make it hard to use outdoor space.
If you have symptoms such as fever, rash or joint pain after travel, talk to a doctor and mention where you traveled.
Local Examples: Costa Mesa and Garden Grove
In Costa Mesa, many people assume their mosquitoes come from Upper Newport Bay or the Santa Ana River. Those wetlands are monitored by the vector control district, and the daytime biters on Eastside patios and Mesa Verde backyards usually come from potted plants, fountains and clogged drains much closer to home. Our Costa Mesa mosquito control page lists the breeding spots we find most often there.
In Garden Grove, where invasive Aedes were confirmed in 2015, the flat, closely spaced lots and productive backyard gardens with buckets and rain barrels give these mosquitoes plenty of places to breed. Our Garden Grove mosquito control page explains why neighbors' yards matter so much in that city.
Do Citronella Candles, Zappers and Traps Help?
Most backyard gadgets do little against invasive Aedes. Bug zappers attract insects with light, but Aedes are drawn to people, not to light, and zappers mostly kill harmless insects. Citronella candles offer limited protection only very close to the flame. Some traps designed specifically for Aedes can catch a portion of the local population, but they work best as a monitoring tool alongside container removal, not as a replacement for it.
What does work is the combination of removing breeding water, keeping shaded resting areas trimmed or treated, and using an EPA-registered repellent on your skin when you are outside.
How to Stop Daytime Mosquito Bites
Remove and scrub containers weekly. This is the single most effective step and costs nothing.
Repair window and door screens so mosquitoes stay outside.
Use an EPA-registered repellent when you are outdoors, following label directions.
Run a fan on the patio. Aedes are weak fliers and struggle in moving air.
Trim dense, shaded vegetation near seating areas so there are fewer resting spots.
Report neglected pools and request free mosquitofish for ponds through the Orange County Mosquito and Vector Control District at ocvector.org or 714-971-2421.
When to Call a Professional
If you have done the weekly container routine and are still getting bitten, the source may be hidden in your yard or coming from nearby properties. A professional mosquito treatment includes a full breeding-site survey, larvicide for water that can't be removed, and an EPA-registered barrier spray applied to shaded resting areas according to the label. During the May through October season, monthly visits typically cost $100 to $175 per month, and a one-time treatment runs $150 to $300.
Yogi's Pest Control is licensed by the California Structural Pest Control Board (OPR 14866) and serves all of Orange County 7 days a week. Call 714-323-8262 for a free mosquito inspection.
