Alphabet’s life sciences arm, Verily, says it has built a robot that can raise a million mosquitoes a week and has used it to produce infertile male insects. The company has started releasing the first batches of what will total 20 million sterilized mosquitoes in Fresno County, California.

This field trial is expected to be the largest U.S. release to date of male mosquitoes treated with Wolbachia, a type of naturally occurring bacteria that infects many types of insects. Verily says it is using custom-built software algorithms and machines to ramp up the number of mosquitoes it’s able to grow and release. The mosquitoes are part of the company’s plan, announced last October, to fight diseases like Zika and dengue fever.

Verily’s effort represents a growing interest by industry and nonprofit organizations in using altered insects to stop the transmission of deadly diseases and protect crops from agricultural pests. The Bill and Melinda Gates Foundation is also exploring the idea of sterilized mosquitoes, and the U.K. company Oxitec is genetically engineering moths with a gene that makes the insects die off over time (see “Are Altered Mosquitoes a Public Health Project, or a Business?”). 

To help breed and release the mosquitoes, Verily has partnered with Kentucky-based Mosquito Mate and Fresno’s mosquito control agency, the Consolidated Mosquito Abatement District. The mosquitoes the company is making aren’t genetically engineered. Rather, they’re bred to be infected with the bacteria, which essentially sterilizes them. When the treated males mate with females in the wild, the females’ eggs aren’t able to develop properly and don’t hatch. The idea is that the sterile males will help deplete the local mosquito population. Male mosquitoes do not bite humans and cannot transmit disease to people, so Verily and its partners aim to release only males. The company has created an automated sex-sorting process to lower the risk that females will end up in the mix. 

Mosquito Mate has previously conducted smaller field studies in Los Angeles and the Fresno area, among other locations, but Verily’s high-tech approach will allow for the release of one million mosquitoes a week, 25 times more than the Kentucky company was able to do before. The male mosquitoes will be released over 20 weeks in two neighborhoods of about 300 acres each using an automated device, also built by Verily. Mosquito Mate’s earlier releases of modified mosquitoes were done by hand using plastic containers. 

Linus Upson, a senior engineer at Verily, says the purpose of the study is to see if the approach succeeds at reducing the population of mosquitoes in the area where the bacteria-treated insects are released. He says Verily’s automated approach could help lower costs for communities wanting to control mosquitoes this way.

“If we really want to be able to help people globally, we need to be able to produce a lot of mosquitoes, distribute them to where they need to be, and measure the populations at very, very low costs,” Upson says. He declined to give any cost estimates.

Verily is using a line of modified Aedes aegypti mosquitoes—the species that carries chikungunya, dengue, yellow fever, and Zika viruses. Mosquito Mate founder Steven Dobson originally created the insects 15 years ago by injecting newly laid mosquito eggs with Wolbachia using a tiny needle. The infection has been transmitted through female mosquitoes ever since, so there’s no need to inject each new generation. Wolbachia, which has been relatively well studied as a mosquito-sterilizing technique, doesn’t infect humans and can’t be transmitted to humans through an insect bite.

The modified mosquitoes are regulated through the U.S. Environmental Protection Agency as “microbial pest control.” In an ecological risk assessment conducted in 2016, the agency said Mosquito Mate’s altered mosquitoes are not expected to cause any harmful effects to other organisms, including endangered species.

Upson says Verily also plans to conduct a field trial in Australia later this year. “We want to show this can work in different kinds of environments,” he says.