To enhance our integrated approach to mosquito management, Orange County Mosquito and Vector Control District (OCMVCD) is evaluating the Sterile Insect Technique (SIT) as a biological control method to lower Aedes aegypti populations and reduce the risk of disease transmission. Our SIT project utilizes an environmentally safe and biologically sound approach to mosquito control that fights mosquitoes with mosquitoes.

OCMVCD uses x-rays to sterilize male mosquitoes, which do not bite or spread disease, and then releases them into the project area to mate with wild female mosquitoes. The resulting eggs do not produce mosquito offspring, thereby reducing the mosquito population in the immediate vicinity.
 

Frequently Asked Questions (FAQs)

What is SIT?

The Sterile Insect Technique, or SIT, is a biological method of mosquito management. This process involves using a limited dosage of x-rays to sterilize male mosquitoes, after which they are released them into the wild. When the sterilized males mate with wild females of the same species the resulting eggs will not hatch. SIT has been used to combat mediterranean fruit flies in Los Angeles, Riverside, San Bernardino, and Orange Counties since 1996.

What type of mosquitoes are you targeting? 

We are targeting invasive Aedes aegypti  mosquitoes (popularly known as "ankle biters"), which have proven resistant to mosquito control methods. Aedes aegypti  are aggressive day biters that have the potential to transmit dengue, Zika and yellow fever viruses to humans.

Will the SIT mosquitoes you release bite me?

No! Male mosquitoes do not bite and they can't spread disease. Female mosquitoes bite because they require nutrients from blood to assist in egg production. Since male mosquitoes do not produce eggs, they do not require a bloodmeal and do not bite. Only female mosquitoes bite.

Are SIT mosquitoes harmful to humans or other organisms?

SIT is a form of biological and species-specific control. Aedes aegypti is an invasive mosquito species that thrives in urban areas and is not an essential part of the natural ecosystem. Reducing or eliminating the population of this mosquito will not harm native insect-eating animals. Because SIT specifically targets Aedes aegypti mosquitoes, it leaves non-target species, such as bees and butterflies, unharmed. These mosquitoes pose no risk to birds, bats or any other wildlife if they are consumed. Because male mosquitoes do not bite, they also pose no risk to humans and cannot transmit disease.

Are these mosquitoes genetically modified?

No. These mosquitoes are locally sourced from Orange County and bred in captivity. The male mosquitoes are then sterilized using low dose x-rays and released. There is no genetic modification involved in this process.

Why are you starting this program now? And why only in Mission Viejo?

OCMVCD is constantly improving our processes and control methods to provide the best possible service for the residents we serve. We are committed to exploring innovative mosquito control strategies that can be incorporated into our integrated mosquito management program. This pilot project will allow us to explore the use of SIT to control Aedes aegypti mosquitoes that are resistant to other treatments and reduce the risk of disease.

Mission Viejo was selected for this program because Aedes aegypti are prevalent in the area. This species is commonly referred to as a “backyard breeder” as it prefers to lay its eggs in small areas of contained water such as buckets, children’s toys, tires, plant saucers, etc.

Will you be releasing mosquitoes in other parts of Orange County?

The results of this program will be monitored and analyzed through 2026. If the program is successful in lowering Aedes aegypti populations, it may be expanded to other urban areas of the county where Aedes aegypti is prevalent.

Can I request SIT mosquitoes be released in my neighborhood?

OCMVCD uses a precise approach to provide the most appropriate treatments for each area of the county based on the species of mosquito and habitat in the area. There are currently no plans to allow residents to request SIT releases in their neighborhood, but if the program is successful, we will look into expanding it to other appropriate areas beyond Mission Viejo.

Will SIT replace the insecticides used by mosquito control?

No, SIT and other innovative control methods will not replace traditional mosquito control methods. SIT has the potential to be integrated with other mosquito management strategies to strengthening our control efforts against mosquitoes that transmit disease. All of these strategies work together through an integrated mosquito management approach to provide the best results.

Will SIT releases impact normal mosquito control treatments?

SIT may reduce the need for other mosquito control methods targeting Aedes aegypti as populations are brought down, but it will not reduce the need to control other species of mosquito.

Do other areas in California use this technique for mosquito control?

Mosquito control programs in Los Angeles and Fresno counties have had success using SIT to complement their mosquito control efforts.

How will you know that the program is working?

We will be setting mosquito traps in Mission Viejo to collect mosquito eggs as well as adult mosquitoes. This trapping will occur in areas where SIT mosquitoes will be released (SIT intervention zone) as well as areas where SIT mosquitoes will not be released (control zone). By comparing the hatching rate from collected eggs and adult Aedes aegypti numbers in the SIT intervention zone to control zone, we will be able to gauge the level of success of the program.

What can residents do to help OCMVCD help combat this invasive species? 

Mosquito control is a shared responsibility. Everyone must take charge of their yard and eliminate standing water and unneeded containers weekly. Residents can sign up to become a mosquito advocate in their neighborhood to educate their community: https://www.ocvector.org/become-a-neighborhood-advocate.

If you have any other questions about Sterile Insect Technique or other methods of mosquito control, please email us at ocvcd@ocvector.org.