California releases half a million male mosquitoes to curb extended season

Nearly half a million male mosquitoes infected with a Wolbachia bacterium arrived in the San Gabriel Valley, east of Los Angeles, as part of California’s expanded vector‑control effort. The insects were shipped in a single box containing 25 paper tubes roughly the size of toilet‑paper rolls, a delivery confirmed by Tristan Hallum, who oversees scientific programs for the San Gabriel Valley Mosquito and Vector Control District. The release follows earlier pilot projects that introduced Wolbachia‑carrying males to compete with wild females, thereby reducing the population of disease‑transmitting mosquitoes.

The district plans to disperse the insects over the coming weeks, aiming to suppress local Aedes aegypti and Aedes albopictus populations that can spread dengue, Zika and chikungunya viruses. By releasing only males, which do not bite, the program seeks to lower disease risk without direct human exposure. Officials will monitor mosquito counts and infection rates to assess the impact of the nearly 500,000‑strong deployment, which represents the latest phase of a statewide strategy to curb vector‑borne illnesses.