Frequently Asked Questions

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  • What is a vector?

    Vectors are insects or other animals capable of transmitting the causative agent of human disease. Some examples of vectors in San Diego County are mosquitoes, ticks, and rats. "Vector” also includes eye gnats. The State of California also defines a vector as an animal that is capable of causing discomfort or injury.

  • What is the Vector Control Program?

    The Vector Control Program (VCP) is part of the County of San Diego Department of Environmental Health and Quality (DEHQ) that monitors and controls vectors such as mosquitoes and other disease-carrying arthropods (like ticks), and rodents in the county.

    The VCP operates under the authority of the Mosquito Abatement and Vector Control District Law of the State of California (Health and Safety Code Section 2000-2093), which details the need and rationale for creating Mosquito Abatement and Vector Control Districts in the State.

  • What is Integrated Vector Management (IVM)?

    Integrated Vector Management (IVM) is a strategy used by vector control districts throughout California and the United States to maximize control of vectors and protect public health using the “lightest touch” possible. It is an evidence-based, data-driven, multifaceted approach that consists of many complementary techniques including:

    Public Education and Outreach

    The VCP conducts extensive public education and outreach to educate residents about vectors and vector-borne diseases so that residents are empowered to take actions to reduce vectors at their homes and protect themselves from vector-borne diseases.

    Surveillance and Monitoring

    Vector populations, their habitats, infection status, and other factors are routinely monitored to assess their risk to public health and to choose the best methods to control vectors before major problems arise.

    Disease Diagnostics

    Vector specimens are tested for numerous diseases that could pose a risk to public health. Test results are used to help inform appropriate actions to protect public health. When necessary, new tests are utilized or developed to detect emerging diseases.

    Source Reduction

    Source reduction reduces places that vectors breed and live so that vectors are reduced or eliminated. Source reduction for mosquitoes primarily involves physical elimination or reduction of standing water, vegetation management, water control, and other maintenance activities.

    Source Treatment

    Source treatment for mosquitoes involves reducing vectors using biological controls such as mosquito fish and organic and naturally-occurring bacterial larvicides, as well as carefully selected EPA-approved products, such as synthetic larvicides and adulticides, to reduce larval and adult mosquito populations. 

  • What services does the Vector Control Program provide to the public?

    In addition to monitoring and controlling vectors such as mosquitoes throughout San Diego County, the Vector Control Program (VCP) also responds to complaints about vectors and requests for inspections.

    San Diego County residents can report high levels of mosquito activity, as well as potential sources of mosquito breeding, such as green pools, to the VCP. Residents can also request an educational mosquito and/or rat inspection. A VCP technician will contact the resident within 3 business days and arrange to inspect the property for signs of mosquito breeding or rat activity and provide recommendations for prevention. In the case of a rat inspection, a free rat control starter kit will be provided.

    Local groups can also invite the VCP to attend community fairs and events, and to give presentations at schools and meetings to provide education and information about vectors and how the public can stay safe from vector-borne diseases.

    The VCP also provides mosquito fish free of charge to San Diego County residents for the purpose of mosquito control in artificial sources of water such as backyard fountains and ornamental ponds.

    VCP services can be requested by calling (858) 694-2888 or emailing You can learn more about these services at

  • What vectors and vector-borne diseases are present in San Diego County?

    Some examples of vectors in San Diego County are mosquitoes, ticks, rats, and other rodents. "Vector” also includes eye gnats.

    In San Diego County, there are at least 9 species of mosquitoes known to carry diseases that can be passed to humans. Native Culex mosquitoes can transmit West Nile virus and tend to bite during dusk and dawn. Invasive Aedes mosquitoes bite during the day and can transmit Zika, dengue, yellow fever, and chikungunya viruses.

    Rats are common pests in and around people’s homes and can spread disease, contaminate food, and cause costly structural damage.

    Wild deer mice are the main carriers of hantavirus. Rodents such as ground squirrels, chipmunks, and wood rats (and their fleas) can transmit plague bacteria to humans. These rodents do not typically live with people but are monitored by the VCP.

    Ticks can carry and transmit vector-borne diseases such as tularemia, Rocky Mountain spotted fever and Lyme disease. The Vector Control Program routinely collects, identifies, and tests ticks for these diseases.

    Eye gnats are small, shiny black flies that, in large numbers, can be an annoyance to both people and animals.

  • What kind of methods does the Vector Control Program use for mosquito control?

    The Vector Control Program (VCP) uses integrated vector management, a data-driven, “lightest touch first” approach to mosquito control. The program controls mosquitoes to protect public health, while using methods with the least amount of impact to the environment possible.

    This approach prioritizes preventative methods, including outreach and education, and the reduction of sources of mosquito breeding (sources of stagnant water). When appropriate, biological control methods such as adding mosquito fish to artificial sources of water (such as backyard pools and ornamental ponds) are used as well.

    Other biological control methods include using bacterial mosquito larvicides when necessary. These bacterial larvicides are made from naturally occurring bacteria and/or bacterial byproducts and are applied by State-certified, trained technicians on the ground as well as by a special helicopter as part of the VCP’s aerial larvicide applications. Products approved for use in organic production (OMRI listed) are used whenever possible; in 2021 more than 94% of the product applied by the VCP (by weight) met this standard. These bacterial larvicides kill mosquito larvae (before they can become biting adults) but are safe to people, plants, and wildlife.

    Chemical control of larvae is used for immature mosquitoes in water when biological control and source reduction are not possible. Adulticides are products that rapidly reduce adult mosquito populations. This can be necessary when larval control measures no longer reduce the presence of biting-adult mosquitoes, or there is significant threat of disease transmission in an area. The use of adulticides is determined by thresholds in the VCP’s strategic response plans.

    All products used are EPA-approved and applied by trained Certified Vector Control Technicians certified by the Vector-Borne Disease Section of the California Department of Public Health (DPH). Certified technicians also complete required continuing education hours every two years. 

  • What is a Program Environmental Impact Report (PEIR)?

    An Environmental Impact Report (EIR) is a report that informs the public of the potential environmental effects of a proposed project, determines ways to minimize any potential effects, and describes reasonable alternatives to the specified project.

    A Program Environmental Impact Report (PEIR) is a type of EIR allowed under the California Environmental Quality Act (CEQA) that is used to evaluate a plan or program that has multiple components or actions that are related either geographically, through application of rules or regulations, or as logical parts of a long-term plan. 

  • Why is the County preparing a PEIR?

    The County is proposing an enhanced Integrated Vector Management Plan (IVMP) to strengthen its ability to protect residents from existing and new invasive vectors and emerging vector-borne diseases. The PEIR is intended to allow the County to examine potential environmental effects of the proposed IVMP and communicate those findings with the public. It will include a discussion of best management practices (BMPs) to avoid and/or minimize potential impacts and explore additional mitigation measures to reduce potentially significant impacts associated with the IVMP. 

  • How can I learn more about the Vector Control Program or the PEIR?

    To learn more about the Vector Control Program (VCP) as well as vectors and vector-borne diseases in San Diego County, please visit the VCP website at If you have any questions about the program, please contact us at (858) 694-2888 or

    Updates on the Program Environmental Impact Report (PEIR) and the public comment period will be posted on the Integrated Vector Management Plan website and on Engage San Diego County. You can also subscribe to email updates regarding the program. 

  • How do I submit comments on the PEIR?

    Once the Program EIR is published for public review, written comments will be accepted by mail and e-mail. 

    Updates on the Program Environmental Impact Report (PEIR) and the public comment period will be posted on the Integrated Vector Management Plan website and on Engage San Diego County. You can also subscribe to email updates regarding the program.