Why you should be glad 500K mosquitoes are being released in San Gabriel Valley

The San Gabriel Valley is heading into peak mosquito season. If a new program goes well, there'll be even more of the pesky fliers than normal — and that's a good thing.

The San Gabriel Valley Mosquito and Vector Control District is releasing more than 480,000 mosquitoes over the next few months, with an aim to squash the invasive ankle-biters known as Aedes aegypti mosquitoes.

What’s happening

The San Gabriel Valley is one of the L.A. County areas that regularly get a lot of mosquitoes, but every season can be different. As well as being a major outdoor annoyance, Aedes aegypti is the primary carrier of dengue, and while local transmission is historically very low, the species is tough to kill off because their eggs can survive in tiny amounts of water.

That’s why the district is using a technique that introduces sterile insects into the mix. The mosquitoes they’re releasing between now and October are males that carry Wolbachia, a naturally occurring bacteria that makes them unable to have offspring with wild females.

Male mosquitoes don’t bite, so while residents may see more of them, they won’t leave a trail of those itchy bumps.

It’s a technique that’s been used elsewhere in SoCal, including San Bernardino County, with some success.

They’re going to the unincorporated community of Basset, just south of Baldwin Park, because it historically sees more activity. The area averaged more mosquitoes per trap than the district’s service area between 2020 and 2025, according to Anais Medina Diaz, communications director for the district.

Over 16 weeks, these urban bloodsuckers will be released from cardboard tubes in a 25-acre area between the intersections of East Temple Avenue, Millbury Avenue, Moccasin Street and Vineland Avenue.

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Courtesy the San Gabriel Valley Mosquito and Vector Control District

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They likely won’t travel much farther beyond that. Aedes aegypti populations are known for being short-distance flyers, covering about a tenth of a mile in their lifetime.

Why now?

Mosquitoes are becoming a year-around problem for Southern California, but there are still peaks to the season.

For the San Gabriel Valley, Medina Diaz said the higher Aedes activity happens between August and October.

The district’s program is also lasting longer than other programs in L.A. County for a specific reason. They want to increase the chances for sterile males to mate with wild females, which can live up to two months, according to the district.

By stopping new female Aedes aegypti mosquitoes from being born, Medina Diaz said they hope residents won’t have to deal with as many bites.