COVID-19: Important Update Regarding Changes in District Services


We continue to provide our essential services for protecting public health by working to prevent vector-borne disease in Contra Costa County; however, the following changes are in effect until further notice in an effort to reduce the risk of COVID-19 transmission:

  • The District continues to provide our other services to reduce the risk of vector-borne disease while implementing these important steps to reduce the risk of COVID-19 transmission:
    • District employees wear face coverings upon initial contact with a resident during an inspection and maintain a 6 foot distance from residents or other citizens present during a District service. If the resident agrees, the District employee will remove the face covering during exterior inspections.
    • District employees will conduct exterior inspections for mosquitoes, rats, mice, skunks, ground-nesting yellowjackets, and bees.
    • District employees will only provide an interior inspection of a home or other structure if clear ventilation is available such as in a garage with the garage door open or an exterior shed or structure.
Mosquitoes Bees
Mosquitofish Entomology Laboratory
Rats and Mice Environmental Projects
Skunks Public Affairs Department
Ground Nesting Yellowjackets Integrated Vector Management


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.

Upon request for service, the District will inspect your property for mosquito problems and provide advice on controlling their populations.

With 23 different kinds of mosquitoes that inhabit a variety of water sources, it’s important that the homeowner or caller provide our District employee with a mosquito sample that can be identified to determine its possible source, however we will still be able to provide service without a one (results may be limited without a sample). Simply swat a mosquito and save it or tape it to a piece of paper for the District employee.

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.


image Mosquitofish

Mosquitofish are 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 request, 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.


image Rats and Mice

Homeowners, business owners or any group in Contra Costa County can request a site visit to assist them with rodent issues by phoning the District or making an online service request.

District services include advice for prevention and control.

District employees do not bait nor set traps, but provide valuable, detailed information, guidance and recommendations.


imageSkunks 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 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.


The District does not provide services pertaining to bats. Please click here for resources regarding bats.


image 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. The nest’s location must be identified and the location shared with District employees. This can be achieved by drawing a map, pointing a garden tool, 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. 


image 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. Click here for more information.

As of April 1, 2010, the District no longer tests 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 can be found by clicking here.


Bees (European and Africanized honey bees)

All honey bees are beneficial insects that are essential for 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 majorities 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 nor 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 in an effort to protect their colony.

District services for bees are very limited. 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 center. 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.


image 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.


image 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 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.

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