• Fact: Mosquito-borne diseases are transmitted through the bite of female mosquitoes. Only male mosquitoes are sterilized and released into the wild. Male mosquitoes do not have mouth parts that allow them to break our skin. They only feed on nectar. Released sterile male mosquitoes’ sole focus is to seek out and mate with wild females, but because they can’t bite, they can’t transmit diseases.

• Fact: Genetically modified (GM) mosquitoes (specifically, self-limiting genes) are only one of several Sterile Insect Technique (SIT) approaches to control certain species of mosquitoes. 
  • What’s being modified: Self-limiting GM mosquitoes contain two lab-inserted genes. One gene kills all female mosquito offspring (the control method)  and the other makes the insects glow under a specific type of light (a marker) and allows vector control to identify any self-limiting GM males caught in the wild. 
  • How it works: GM eggs produced in the lab are introduced to an area with high numbers of wild mosquitoes. The GM eggs quickly hatch and emerge as adults. The GM female mosquitoes die (because they contain the fatal gene) and the GM males live on to mate with wild females and pass their female-fatal gene to their offspring. With only male mosquitoes surviving, there are not enough live females to support the population and the population is reduced. 
  • Impact to the environment: The genes are specific to one species of mosquito and won’t affect or be passed on to other species of mosquito or other insects. Birds and other predators are not affected by eating GM mosquitoes.
  • Regulations: GM mosquitoes are regulated by the EPA.
  • See: CDC “Genetically Modified Mosquitoes” for more information.
  • Other common SIT programs may use irradiation or a bacterial agent to modify males and achieve population control. 

Fact: SIT programs only focus on one species at a time. The technique uses insects of the same species as the target pest that already lives in the environment. It does not introduce a new species into the ecosystem.

• Fact: Male mosquitoes do not bite and cannot transmit disease. Flooding an area with sterile males increases the odds a wild female will mate with a released male. While you may notice more non-biting male mosquitoes during a release, these males do not contribute to the bites residents are experiencing. Overall, the goal of the technique is to reduce the biting female population over the long term.

• Fact: SIT using GM self-limiting genes only affect the target mosquito species. There is a small chance that the self-limiting gene could be passed on to a different but related mosquito species if cross-species mating occurs. But field tests found that the self-limiting gene tends to die out after several generations within the same species, and hybrid offspring are usually sterile. Mosquito-eating predators cannot pick up the gene from eating a mosquito containing a self-limiting gene. Pollinators such as butterflies and bees cannot be “infected” or affected by close contact with GM mosquitoes feeding from the same nectar sources.

• Fact: Backyard mosquitoes tend not to have many predators eating them, which is why there are so many mosquitoes. SIT, like so many other mosquito control techniques, has a temporary effect on a very local population of mosquitoes. Since mosquitoes are just one small part of a varied diet for insect-eating predators, a temporary reduction in mosquitoes will result in predators switching to other species of insects for food. 

• Fact: SIT often requires repeated releases over time to be effective, especially in areas where getting rid of standing water where mosquitoes grow (source reduction) is a challenge. Sterile Insect Technique may be an ongoing process in certain areas and under certain circumstances to suppress pest populations.

• Fact: SIT programs have a safe and effective track record in other states and in multiple countries for the past 70 years. In the U.S., the approval process for Sterile Insect Technique (SIT) involves both state and federal agencies, uses a phased approach guided by international safety guidelines and principles, and focuses on data collection, risk assessment, and integration with existing pest management. Use of SIT requires permits and applicators must demonstrate safety and efficacy before area-wide releases can be made.

• Fact: SIT is, currently, a more expensive control method than other methods (eg: source reduction, larval control). There is no funding mechanism to use SIT on a large scale. As one type among many control tools, SIT is appropriate for a certain set of conditions and not appropriate for others. SIT is seen as a proactive measure and not the best tool to address public health emergencies.