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Services and Programs

District services and programs for Contra Costa County residents are funded by your tax dollars and are provided at no additional cost. Our services and programs include:


Our county’s diverse ecological regions create a range of mosquito sources. The District regularly surveys more than 10,000 acres of marshland along the waterfront, acres of irrigated farmland in the eastern county, and numerous ponds, creeks, and residential sources countywide in an effort to control the species of mosquitoes currently in existence while also on the lookout for the potential arrival of new and invasive mosquito species. The county is also home to many insects that resemble mosquitoes.

Insects Commonly Mistaken for Mosquitoes

Upon a request for service, the District will inspect your property for mosquito problems and provide advice on controlling their populations. This may include the placement of 


Mosquitofish are also available by request for private ponds, horse troughs, non-maintained swimming pools and spas, rain barrels, and more (you must be a Contra Costa County resident). Mosquitofish can eat several hundred mosquito larvae per fish per day. Upon a request for fish, the District will inspect your water feature and determine if mosquitofish are appropriate to address the mosquito issue on the property. If fish are an appropriate option, the District employee will place the fish in the water feature.

Swimming Pools and Spas

The District also appreciates Contra Costa County residents doing their part to protect public health by reporting non-maintained swimming pools (pools that are not chlorinated or filtered). Residents can submit swimming pool reports anonymously by phone (925) 685-9301 or online.

Not only are they unsightly, but neglected pools and spas can pose a threat to public health. Mosquitoes need very little standing water to complete their life cycle. Swimming pools and spas that are not maintained can be an ideal source for more than 1 million mosquitoes that may go on to become infected with West Nile virus. These mosquitoes may affect people up to five miles away. While having a green swimming pool is not illegal, it is illegal to produce mosquitoes. 

Rats and Mice

Residents in Contra Costa County can request a site visit to assist them with rodent issues by calling the District or making an online service request.

Service for rats and mice consists of an exterior inspection of a residential property.

District employees do not bait nor set traps, but provide valuable, detailed information, guidance, and recommendations. A resident must call for an inspection of their own property.

Skunks and Rabies Risk Reduction

The District provides inspections and assistance to reduce the likelihood that humans come in contact with skunks because they are a vector of rabies. Upon the first visit, the technician will inspect the property to determine if a skunk has taken up residence.

To request a skunk inspection, call 925-771-6186 or request service online.

If trapping is necessary, the technician will provide guidelines and policies set forth by the California Fish and Wildlife code to help capture the target skunk.

If you smell a skunk, see a skunk passing through the yard or your pet has been sprayed by a skunk while on your property, please note these occurrences alone do not meet the District's criteria and District employees will not trap nor remove a skunk from your property.

Ground-Nesting Yellowjackets

Yellowjackets are beneficial insects that eat garden pests and pollinate crops through daily foraging; however, they are also considered a vector since they can cause people discomfort or be dangerous to individuals who are allergic to their venom.

The District provides inspection and treatment of ground-nesting yellowjackets since these species are aggressive toward people. We do not provide a service for other species of yellowjackets, nor those that make their nest on or in structures.

For ground-nesting yellowjackets, simply locate the nest and call us for service or make an online service request. If the nest’s location is known, please share that information with District employees. This can be achieved by drawing a map and affixing it to the front door of the residence, pointing a garden tool in the direction of the nest, or identifying the site with a marker (red sock, garden glove, etc.). Once you have requested District service do not attempt to do anything to the nest. The nest must be dry and untreated for the District to treat it. 

Ticks and Lyme Disease

The District provides identification of ticks and biting or stinging pest samples submitted by Contra Costa County residents. Contra Costa County Residents may send a tick or pest sample to the District. 

The District does not test ticks for Lyme disease that are brought in by the public. Lyme disease testing is conducted for surveillance purposes only. A list of local laboratories that will conduct Lyme disease testing on ticks can be found by clicking here.


All honey bees are beneficial insects that are essential for the pollination of many native California crops and plants. If a bee swarm does not present an immediate threat, it is best to leave it alone. The vast majority of bee swarms in Contra Costa County are ordinary European honey bees in pursuit of a permanent home and are docile unless provoked.  Both European and Africanized honey bees are non-aggressive in this stage as they are not protecting their honey or their hive. The swarms typically move away in a day or two. Do not kill, swat, or threaten the bees because that may cause them to release a pheromone that incites other bees to become aggressive to protect their colony.

District services for bees are minimal. The District does not respond to bee-stinging incidents. In the case of a bee stinging incident that requires emergency services, please call 911 for assistance. We treat bee swarms or hives that are a threat to people in public areas such as a school or shopping centers. The District does not treat bee hives that are in or on a structure or on private property. The District does not determine if bees are Africanized or European.

For help with bee swarm collection/removal, please visit the Mount Diablo Beekeeper’s Association online or contact a colony removal specialist or a private pest control company.

Biting/Stinging Insect Identification

Our public health agency provides an identification service for ticks, mosquitoes, and other stinging/biting pests only. The resident can bring a sample to the District office to request identification, or mail a sample to the District by placing it in a sealed zipper baggie or other sealed container, placing it in an envelope, and providing full contact information including an email address or phone number.  In most cases, you will be notified of identification results within two business days.

Please note: residents must live in Contra Costa County, and must provide an actual sample of the pest itself for identification (we do not accept other materials such as bedding, carpet, etc). We only provide identification of the sample that has been provided and information on potential health risks or prevention, we do not provide testing services. We cannot recommend specific pest control products (brands) or pest control companies. 

For identification or questions about non-biting household garden or crop pests, other resources are available including UC Extension and the Contra Costa County Department of Agriculture.

Entomology Laboratory

The mission of the Marilyn Milby Entomology Laboratory is to protect the public from vector-borne disease and injury by monitoring, analyzing and anticipating disease and vector distribution through surveillance and research; to ensure that the District has control programs that are effective and environmentally sound, and to serve as a credible and accessible information resource for other District programs, the public and other agencies.

Environmental Projects

In addition to protecting public health, the District is also dedicated to protecting the natural environment. Healthy wetlands support populations of natural predators, producing fewer mosquitoes than habitats modified or damaged by human activity. The District plays a leadership role in the conservation and restoration of Bay Area wetlands, protection of endangered and threatened species, and promotion of biorational (environmentally compatible) control methods in order to protect both human and environmental health.

Public Affairs

The Public Affairs Department personnel work closely with county constituents. Public Affairs staff provide literature and presentations to various groups and school children of 12 or more people. The presentations can provide general District information or tailored information. Public Affairs Department personnel also participate in a variety of events, workshops, and community discussions.

Integrated Vector Management

Integrated Vector Management (IVM) is an ecosystem-based strategy, which focuses on the long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and the use of resistant varieties.

Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism.

Pest control methods are selected and applied in a manner that minimizes risks to human health, beneficial and non-target organisms, and the environment.