What is SIT and how does it work?

Sterile Insect Technique (SIT) is a biological mosquito management method that involves releasing sterilized local male mosquitoes to help reduce invasive mosquito populations as part of an integrated vector management strategy.  SIT is used to help control certain mosquito species while reducing the use of traditional insecticides. In this process, mosquitoes are raised in a laboratory, where male mosquitoes are separated from females. The male mosquitoes, which do not bite, are sterilized using radiation.

The sterile male mosquitoes are then released into the community, where they mate with wild female mosquitoes. The eggs produced do not hatch, which can help reduce the number of mosquitoes over time.

According to the Centers for Disease Control and Prevention (CDC), irradiated mosquitoes cannot make people or animals, including fish, birds, or pets, sick.

 

What type of mosquitoes are you targeting?

We are targeting the invasive Aedes aegypti mosquitoes. These mosquitoes are aggressive daytime biters and can spread viruses that cause diseases like dengue, Zika, and chikungunya. They can also spread heartworm in pets.

 

Will the SIT mosquitoes you release bite me?

No. Only male mosquitoes are released, and male mosquitoes do not bite or spread disease. 

Male mosquitoes feed on plant sugars and nectar. Female mosquitoes are the ones that bite people and animals because they need blood to produce eggs.

 

Are SIT mosquitoes harmful to humans or other organisms?

No. SIT targets invasive Aedes mosquitoes, which are not native to California. These mosquitoes are considered an invasive species and are not a natural part of California’s ecosystem.

Reducing invasive mosquito populations is not expected to harm animals that eat insects, including birds, fish, bats, and other wildlife native to California.

 

Are these mosquitoes genetically modified? 

No. These mosquitoes are collected from our local service areas, raised in a laboratory, and sterilized using X-ray technology. No genetic modification is used in this process.

 

Where are you releasing these mosquitoes?

Release areas are selected by the Northwest Mosquito and Vector Control District using mosquito surveillance data, including the presence and prevalence of Aedes aegypti mosquitoes and suitable habitat conditions.

 

Why are additional mosquito control methods needed for invasive Aedes mosquitoes?

Invasive Aedes mosquitoes often lay eggs in small containers and water sources found in front yards, backyards, patios, and other private areas that our district cannot easily access or inspect.

These mosquitoes have also shown resistance to some commonly used insecticides and continue to spread throughout California.

Additional mosquito control methods, such as SIT, may help control invasive mosquito populations and support public health efforts.

 

Has this proven to be effective?

The California Department of Food and Agriculture successfully used SIT to control Mediterranean fruit fly infestations in citrus and other fruit trees. The United States Department of Agriculture also successfully used SIT to control screwworm flies that can harm livestock.

 

How often are sterile mosquitoes released?

Sterile male mosquitoes are typically released on a regular schedule during mosquito season. Repeated releases are needed because mosquitoes have short life cycles and new mosquitoes continue to hatch over time.

Release schedules may vary depending on mosquito activity, weather conditions, and surveillance data collected by the District.

 

How do you monitor whether the program is working? 

The District monitors mosquito populations using traps and routine surveillance activities before, during, and after mosquito releases. 

Collected data helps staff track mosquito activity, measure population changes, and evaluate the effectiveness of the program over time. 

 

What can residents do to help reduce mosquitoes?

Residents can help reduce mosquitoes by removing standing water around their homes and yards. Even small amounts of water can allow mosquitoes to breed.

Common sources include:

• Flower pots
• Buckets
• Pet water bowls
• Bird baths
• Clogged gutters
• Outdoor containers