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Frequently Asked Questions

For questions and answers regarding Adult Mosquito Control, please click here

Our Services

Q. What services do you provide to Contra Costa County residents and what is the cost?

A. As a public health agency, we provide the following services and programs to all Contra Costa County residents at no additional charge (we are funded by way of property and benefit assessment taxes):

Mosquitoes: Inspection and assistance.

Mosquitofish: Upon request. For backyard pools and ponds - inspection and assistance.

Rats and Mice: Inspection and advice.

Skunks: Inspection and assistance.

Ground-Nesting Yellowjackets: Ground nest treatment (ground-nesting species only).

Bees: Identification and education.

Ticks: Identification: Resident must provide a sample (mail to the District or bring in-person) of the tick for proper identification.

Biting/Stinging Insect ID: Resident must provide a sample (mail or bring in-person) of the insect for proper identification.

Other Insects and Animals

Q. Who should I contact regarding issues I am having regarding squirrels, moles, possums, raccoons, ants, spiders, etc.?

A. Please click here for resources that can help you with insects and animals for which we do not provide service.

Swimming Pools

Q. What authority do you have regarding neglected swimming pools?

A. We appreciate attention to maintaining pools in a manner that does not produce mosquitoes. If the pool or other sources produce mosquitoes, we have the authority to initiate legal procedures pursuant to Civil Code Section 2929.3 and Health and Safety Code Sections 2020 and 204(m). A copy of our Districts’ resolution is available for perusal.

West Nile Virus

Q. Do we expect more human cases this year?

A. We remain confident that our mosquito control program will have a significant impact on keeping human cases to a minimum. No one can predict the number or severity of cases.

Adult Mosquito Control (Notifications)

Q. How do you notify people and why can’t you do it sooner?

A. We have a very comprehensive response plan that relies on real-time data about mosquito populations, virus transmission, and weather conditions. Once we determine there is a risk to the public, we act immediately, sometimes within hours of our decision to conduct adult mosquito control operations, before the mosquitoes fly away and the conditions to control them change. People wishing to be notified about adult mosquito spraying have several options. They may visit the District’s website and opt to receive notifications automatically by email, they can view information on the District website, or they may phone the District for a recorded message at (925) 685-9301. We also work closely with the media, though, they are not always able to publish or announce the information in time of advanced notifications.


Q. How long does standing water need to exist before mosquitoes can begin their life cycle?

A. All 23 species of mosquitoes in Contra Costa County (as well as every species worldwide) require standing water in order to begin their life cycle. Mosquitoes can go from egg to flying adult in as little as five days. Dump or drain cans, buckets, containers - anything on your property that is holding water, to prevent mosquitoes.


Q. Can you deliver mosquitofish to my house?

A. Mosquitofish for backyard ponds and non-maintained swimming pools can be requested by contacting the District by phone or online (must be a Contra Costa county resident). Upon receiving your request for mosquitofish, a District employee will follow up with you and make an appointment for an inspection. During the inspection, the District employee will determine if the water feature is an appropriate location for the fish. If the location is appropriate for mosquitofish, the District employee will place fish in the water feature. If, for example, the water feature is found to be producing more mosquito larvae than the fish can initially handle, the District employee will provide assistance and advice on the appropriate action to mitigate the mosquito issue.

Dead Birds

Q. How come you don’t pick up and test ALL dead birds reported to you?

A. We appreciate all dead bird reports. West Nile virus is a serious disease and reporting dead birds gives us crucial information for our surveillance and control efforts. Not all birds can be picked up and tested, but just the report itself provides crucial information for our surveillance and control efforts.

More About the District

Q. Does your District provide presentations for people who want to learn more information?

A. Our Public Affairs staff provide general and tailored presentations ranging from 10 minutes to one hour to any group of 12 people or more. We provide presentations to groups such as rotary clubs, public works agencies, homeowner associations, city councils, and schools. Presentations and tours are also available at our office in Concord.