Sterile Insect Technique (SIT)

What is Sterile Insect Technique (S.I.T.)? S.I.T. is an environmentally friendly, species-specific method that releases sterilized male mosquitoes to mate with wild females, resulting in nonviable eggs (eggs that do not hatch) and fewer mosquitoes over time. 

An individual uses the Sterile Insect Technique in a natural setting, possibly for pest control in the San Gabriel Valley (SGV).

We're adding a new tool to the mosquito control toolkit. S.I.T. has been successfully used against pests like screwworms, fruit flies, and mosquitoes—and now it’s part of our strategy to better protect our communities in the San Gabriel Valley.

Sterile Insect Technique is just one tool in a holistic, integrated vector management plan

S.I.T. has been used in the United States and around the world since the 1950s to control insect pests. For example, S.I.T. has been used to control Mediterranean fruit fly (Medfly) in Southern California since the 1990s. S.I.T. was also used to eradicate screwworm flies in North and Central America. These methods are still used today.

Download overview of USDA screwworm control program (PDF)

Sterile Insect Technique in the San Gabriel Valley

Person taking a photo of nature with shrubs, mountains, and a clear sky in the background.
Image of SGV Mosquito Staff releasing sterile male mosquitoes.

The San Gabriel Valley Mosquito & Vector Control District supports the evaluation and research of S.I.T. for mosquito control. Federal and State regulatory agencies will determine the safety of innovative approaches in California. 

How does it work?

S.I.T. targets specific types or species of mosquitoes (such as Aedes aegypti or Aedes albopictus). Generally, S.I.T. for mosquitoes involves three steps:

  • Mass production of mosquitoes
  • Sorting males from females
  • Mass release of male mosquitoes into an area.

These steps may differ depending on the type of Sterile Insect Technique. 

The image shows a graphic of a mosquito with the text "Male Mosquitoes Don’t Bite," highlighting a common fact about them.
Male mosquitoes are identifiable by their extra fuzzy antennae.

Male mosquitoes do not bite. Male mosquitoes do not spread diseases.

For a successful Sterile Insect Technique, the sterilized male mosquitoes released into an area must largely outnumber wild male mosquitoes. Once released, S.I.T. male mosquitoes mate with wild females, and because these are sterilized male mosquitoes, no offspring are produced. Over time, the number of the targeted mosquito species in the area is reduced. 

A graph showing the decrease in the number of mosquitoes over time.
Image of mosquito populations decreasing over time due to the use of Sterile Insect Technique. 

S.I.T. for mosquito control can be used as part of an integrated vector management approach. S.I.T. may be a preferred way to reduce the number of mosquitoes in areas where the use of insecticides is not possible or where insecticide resistance has reduced the effectiveness of insecticides.

Male mosquitoes do not bite people or animals. They feed on nectar. Therefore, people living in the release area will not be bitten more than usual.

There are three major types of Sterile Insect Techniques that can have a sterilizing effect on specific mosquito species:

X-Ray (Irradiated) Male Mosquitoes 
Wolbachia the Bacteria 
Self-limiting Gene or Gene Modification