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Frequently Asked Questions(SIT)

What is SIT? 

Sterile Insect Technique (SIT) is an insecticide-free technique used to reduce insect populations. Lab-reared sterilized insects mate with the wild population to reduce the targeted species.

Has SIT been used before? 

SIT is not a new technology. In fact, its first use in the United States occurred on Sanibel Island in 1951 to eliminate the Screwworm Fly. In 2016, sterile screwworm flies were released to successfully control a localized outbreak in the Florida Keys.

Currently, SIT is used in agriculture to control fruit flies as well as the medically-important Tsetse fly, which spreads sleeping sickness pathogens to cattle and humans in Africa.

How does SIT work in mosquito control? 

Female mosquitoes will only mate once in their lifetime. When lab reared sterile male mosquitoes mate with wild female mosquitoes, the female mosquitoes will not produce viable offspring. This will reduce or eliminate the local population through successive releases.

Can the sterile mosquitoes bite people? 

No. With SIT, only sterile male mosquitoes are released, and male mosquitoes do not bite people and cannot alter people’s DNA. These techniques work by releasing sterile male mosquitoes into the environment to mate with wild females of the same species. Females that mate with sterile males lay eggs that do not hatch, and over time, this reduces the number of female biting mosquitoes in the area. The sterile male mosquitoes that are released do not bite - only female mosquitoes bite and are capable of transmitting viruses that cause mosquito-borne diseases.

Will any female mosquitoes be released? 

Male mosquitoes are separated from females and checked for quality control at different life stages to create redundancy and lessen the probability of female release. However, should a female be released into the wild population, they will also be sterile.

Why are new mosquito control techniques needed? 

Invasive Aedes mosquitoes are harder to control because they have become resistant to commonly used insecticides. They lay their eggs in small, hidden water sources in people’s front yards, backyards, and patios — areas where mosquito control agencies can’t easily inspect. Due to the difficult nature of controlling invasive Aedes mosquitoes and the public health risks they pose, mosquito and vector control agencies need additional control methods.

Further, no species acquires immunity to sterile mating like they can with pesticide resistance. The smaller the wild population gets, SIT can continue without risk of pesticide resistance.

Many agencies are exploring the use of Sterile Insect Techniques (SIT) and other innovative technologies to help reduce the population of disease-transmitting mosquitoes.

Is there any genetic modification with this method of control? 

Not in the Coachella Valley. Sterilization is achieved through irradiation (X-rays) and requires no genetic manipulation of the organism. The X-rays used are the same as those used in medical practices and have no residual.

Will the radiation used in SIT harm the environment or other insects? 

No, the level of radiation is similar to use in medical offices and does not have contact transfer or a residual. This technology specifically works to control invasive Aedes mosquitoes which are not originally found in California and don’t have a place in our natural ecosystem. Reducing or controlling these mosquitoes will not harm insect-eating animals that are native to California.

What does it do to bats who eat mosquitos? 

Bats are great insect predators but they prefer moths and beetles over mosquitoes.  Aedes mosquitoes are not originally found in California, so they don’t have a place in our natural ecosystem. Reducing or controlling these mosquitoes will not harm insect-eating animals that are native to California.

What about bees? 

Introducing male mosquitoes will not change the bees habitat because mosquitoes are not in competition with bee food sources.

What about hummingbirds? 

Hummingbirds help reduce insect populations including mosquitoes. SIT research studying effects on non-target species has shown that wildlife such as birds, bees, and butterflies are left unharmed.

Which mosquito will be targeted with the SIT Program? 

The Aedes aegypti mosquito will be targeted, an invasive species in our county. This mosquito is a viable vector of the following viruses: Yellow fever, dengue fever, chikungunya, and Zika.

Aedes aegypti is an urban mosquito, meaning it breeds around homes and prefers to feed on humans. They are difficult to control by conventional means (insecticide applications, source reduction) due to their cryptic behavior and daytime biting habits.

Where can I learn more about the Aedes aegypti mosquito ? 

An invasive urban mosquito is spreading across California, the yellow fever mosquito, Aedes aegypti. These mosquitoes are now found in at least 22 counties throughout the state, including Riverside County and more specifically, the Coachella Valley. Invasive Aedes mosquitoes spread viruses that cause Zika, dengue, chikungunya, and yellow fever. There are no human vaccines for many of these mosquito-borne diseases, and these diseases can have long-term health consequences. These mosquitoes can also spread the parasite that causes heartworm in dogs, cats and other animals, which can lead to severe disease in pets.


Will these techniques replace traditional mosquito control efforts? 

No, SIT and other innovative technologies will not replace traditional mosquito control methods. If used, they will be part of an Integrated Vector Management approach, which is an evidence-based, data-driven decision-making tool used to suppress mosquito-borne diseases. There are many decisions that are made to determine which mosquito control technique will be most effective in different areas and conditions to protect public health. Any emerging technology that is used to protect the public from mosquito-transmitted diseases would be used in conjunction with traditional control methods.

There isn’t an outbreak of Zika or dengue in California, so why do we need to introduce sterile male mosquitoes? 

Due to climate change and increasing global travel and trade, there has been worldwide spread of invasive mosquito species and the diseases they can carry. In California alone, invasive Aedes mosquitoes have spread to more than 300 cities in over 22 counties since their arrival in 2013. Traditional mosquito control methods, including the use of insecticides, show inconsistent and often limited effectiveness against controlling invasive Aedes mosquitoes. This is not specific to California as the World Health Organization’s guidance framework explains that Aedes aegypti have demonstrated resistance to many commonly used insecticides in the Americas, Asia, and Africa and that it is necessary to consider innovative mosquito control methods across the globe.

guidance framework

Mosquito control agencies are on the front lines of mosquito-borne disease prevention and are facing increasing challenges due to the spread of invasive mosquito species. Waiting until these invasive mosquitoes begin to transmit infectious diseases locally in California is not an effective public health strategy. As such, it’s important for mosquito control and public health experts to use a variety of tools that are part of an Integrated Vector Management (IVM) approach to control mosquitoes, prevent the spread of mosquito-borne diseases, and protect public health.

What are the chances irradiated male mosquitoes can transfer radiation to a plant and cause harm to beneficial insects? 

So slim it’s almost none. The dose of radiation is very small. Similar to when you get your teeth X-rayed. Dentists don’t sit next to you when you’re being X-rayed, but they can touch your teeth after without concern of radiation transfer.

How long do sterilized mosquitoes live? 

There is no indication that SIT shortens the lifespan of the adult male mosquitoes. Typically, male Aedes mosquitoes live 1-3 weeks depending on food source (sugars).

Can male mosquitoes inseminate females more than once? 

Female mosquitoes can only mate once in their lifetime. Males can inseminate female mosquitoes more than once although it is unlikely due to the nature of mosquito mating habits in which females tend to become inseminated immediately after emerging from the pupa stage to adult.

What will the SIT program cost? 

There are initial set up costs associate with any new program. Rearing facilities and operation equipment is necessary. Although the SIT program will not replace all traditional use of mosquito control pesticides, it will become an additional tool for product rotation and after initial set up, the cost should remain similar to purchasing chemical pesticides.

When and where will there be a release of sterile male mosquitoes? 

Control areas of release are considered using a variety of data. Mosquito traps are set throughout our service area and regularly survey the number of mosquitoes in each area. Vector Control Technicians also collect data such as larval samples for further information regarding the activity in their zone. Lastly, you are our eyes and ears in the Coachella Valley, if you are experiencing mosquito bites and have closely searched your property for standing water sources, please call and report the issue.  

Will I have a chance to discuss SIT with the District to address my concerns or questions? 

Yes, the District will provide educational talks, classroom presentations in local schools, town hall meetings, and media interviews to answer questions and explain SIT mosquito releases. To request a presentation for your group, please email the district.

Sterile Insect Technique - Spanish Video

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