Mosquitoes Being Released In Lake Elsinore As Part Of Experimental Program

LAKE ELSINORE, CA — Batches of irradiated male mosquitoes are slated for release Wednesday in Lake Elsinore with the goal of pairing the modified insects with as many females as possible to kill off the overall mosquito population, under an experimental program that apparently hasn't generated concerns among public officials.

The "Sterile Insect Technique Pilot Program" is being managed by the Northwest Mosquito & Vector Control District, which serves segments of western Riverside County. The district is believed to be the first countywide to inaugurate an SIT mosquito control program.

Questions regarding when it was authorized, the estimated number of modified mosquitoes that will be released and any potential public health risks were not answered by the agency as of Tuesday afternoon. Lake Elsinore officials also did not respond to requests for comment.

The West Valley Mosquito & Vector Control District, which encompasses Ontario, Montclair and neighboring municipalities in San Bernardino County, was the first district in California to receive authorization from state regulators to initiate mosquito SIT releases last year, under a pilot program similar to that of the Northwest Mosquito & Vector Control District.

It's still unknown whether West Valley's experimental program has netted any benefits.

"Sterile male mosquitoes are released to mate with local females, and the resulting eggs are unable to hatch," NMVCD said in a statement regarding the Lake Elsinore program. "The release of adult male mosquitoes will not increase local bite pressure, as only female mosquitoes bite."

The objective is to thin out Aedes aegypti mosquitoes, which are known to transmit dengue, chikunguya and Zika viruses. The male mosquitoes receive radiation exposure in laboratories to foil their breeding capabilities, according to the International Atomic Energy Agency.

SIT pilot projects have been authorized in other states, including Florida and Texas.

California as a whole has not seen major outbreaks of insect-driven infections in the current century. According to the California Department of Public Health, the number of chikungunya cases in Riverside County from 2016 to July 2025 totaled eight. The agency said that Zika cases countywide over the same period numbered 23. It was unclear from the data whether any of those infections contributed to fatal outcomes.

The Northwest Mosquito & Vector Control District's statement on Wednesday's sterilized mosquito release in Lake Elsinore did not cite achievements using the SIT methods to combat mosquitoes, but instead pointed to the California Department of Agriculture's productive efforts using SIT "to combat the Mediterranean fruit fly."

The U.S. Environmental Protection Agency in 2022 approved plans by British biotech firm Oxitec to undertake a large-scale experimental program that would have entailed releasing several million genetically modified mosquitoes in several California counties. The lab-altered male bugs have the ability to pass on defective genes to gradually eradicate female mosquito populations, according to the EPA.

Oxitec's applications for review by the California Department of Pesticide Regulation were voluntarily withdrawn in 2023. However, the company has ongoing contracts in Florida and other locations worldwide.

It couldn't immediately be confirmed whether the Northwest Mosquito & Vector Control District plans additional releases of modified mosquitoes in Lake Elsinore or elsewhere after Wednesday.