FAQ’s

Have a question? Check our Frequently Asked Questions page for answers.

About Delta Mosquito and Vector Control District

What is Delta Mosquito and Vector Control District?

Delta Mosquito and Vector Control District, founded in 1922, is a special district charged with protecting District residents from mosquito-borne disease and nuisance mosquitoes. Learn more by visiting our About Us page.

What is a special district?

Special districts are local government agencies that provide essential, focused services to meet the community’s needs. They are formed and governed by local residents to establish or enhance essential services and infrastructure.

What does Delta Mosquito and Vector Control District do?

We protect District residents from mosquito-borne diseases like West Nile virus and mosquito nuisances. Key activities include mosquito surveillance, disease testing, integrated vector management, and community outreach.

Why do we need mosquito control?

Mosquitoes are the deadliest animal on planet Earth. According to the World Health Organization, about 725,000 people around the world are killed every year by mosquito-borne diseases. Every year, residents across the United States are infected with mosquito-borne pathogens like West Nile virus, St. Louis encephalitis virus, Eastern equine encephalitis virus, dengue virus and others. In 2019, 184 California residents were infected with West Nile virus. There are no cures for mosquito-borne diseases and only Yellow Fever has a vaccine. Mosquito control is the only way to prevent these deadly diseases.

What areas does Delta Mosquito and Vector Control District serve?

Delta Vector Control District serves most of northern Tulare County including Cutler, Dinuba, Exeter, Farmersville, Goshen, Ivanhoe, Orosi, Traver, Woodlake, most of Visalia, and the unincorporated areas between these cities. You can see our District map here.

How can I tell if I am in your District?

You can view a map of the District here or call our office during work hours at 559-732-8606 or toll-free at 877-732-8606.

How much does Delta Mosquito and Vector Control District charge?

Nothing. No representative of Delta Mosquito and Vector Control District will ever ask you to pay for services.

How do I request services from Delta Mosquito and Vector Control District?

You can complete an online form here or call our office during work hours at 559-732-8606 or toll-free at 877-732-8606.

When are you open?

Regular work hours are Monday through Friday from 7:30 AM to 4:00 PM. The District is closed during holidays.

Where are you located?

The office is located at 1737 W Houston Ave, Visalia, CA.

How can I stay up-to-date with mosquitoes and mosquito-borne diseases in the District?

You can check for news and updates on our website or follow us on Facebook, Twitter, or Instagram.

Mosquito Trap Hosts

What is a trap host?

A trap host is a property where a trap is placed once a week for an entire mosquito season (typically April to mid-October) or for a single night during the year. Residents voluntarily give permission for these traps to be placed on their property and play a crucial role in protecting their communities from mosquito-borne diseases.

Why are trap hosts important?

Mosquito traps provide routine surveillance data about the size of the mosquito population in that area and the presence of mosquito-borne diseases. This information is used by Delta Mosquito and Vector Control District to find and control existing mosquito sources in the area as well as to monitor ongoing control efforts. Visit our Surveillance to learn more about vector and vector-borne disease surveillance.

How are trap hosts selected?

Roughly 5 routine traps are placed per square mile of populated area. Trap hosts are selected to evenly spread these traps across this area. In general, technicians look for properties that have shaded areas such as bushes where a trap can be placed overnight without being disturbed.

Do mosquito traps attract mosquitoes to the area?

No. Mosquito traps catch mosquitoes that are already in the general area of the trap.

I was selected as a trap host. What do I need to do?

You do not have to do anything to be a trap host. A technician will drop the trap off early in the morning once a week and pick it up the next day. Our goal with trap placement and pick up is to avoid disturbing the resident or interfering with their regular activities as much as possible.

I am a trap host and there were a lot of mosquitoes in the trap. Are they all coming from my yard?

No. Traps will collect mosquitoes from the general area. Depending on the mosquito species, they may be coming from a water source that is very close to the trap or one that is farther away. If you are concerned about potential sources in your yard, you can visit our prevention page for tips on what to look for or contact us online here or at 559-732-8606 for a free yard inspection.

What do you do with the mosquitoes you catch?

All mosquitoes are counted and identified to species. These mosquitoes are also tested for viruses if there are at least 10 female mosquitoes of a species that is capable of transmitting West Nile Virus, St. Louis Encephalitis virus, or Western Equine Encephalitis virus. This information is then used to guide our control efforts.

I want to stop being a trap host. Who do I contact?

You may contact the District during regular business hours at 559-732-8606. We would like to thank you for your service to the community and your contribution to keeping District residents free from nuisance mosquitoes and mosquito-borne diseases.

Door Hangers & Notices

Why did I receive a door hanger?

Door hangers are left for a variety of reasons including the need to schedule an inspection/treatment, notification of an inspection, request to set a mosquito trap, and education. Each door hanger has a different color scheme based on how the resident needs to respond. All services are free. Continue reading below to find out more.

I received a Fight The Bite door hanger. What do I need to do?

Fight The Bite Door Hangers

You need to schedule a yard inspection for potential mosquito sources. You can schedule a yard inspection during regular business hours at 559-732-8606 or toll-free at 877-732-8606. This service is free.

 

 

I received a yellow door hanger. What do I need to do?

Check your own yard for common water sources listed on the door hanger and dump them weekly or eliminate the water sources completely when possible. These door hangers mean that the invasive Aedes aegypti mosquito has been found in your area. You do not need to contact the District at this time but, in the future, we may need to inspect your front and backyard for potential sources. Learn what mosquito sources to look for here or fill out an online service request form to request a technician’s help here.

I received a blue door hanger. What do I need to do?

Wait for the scheduled inspection listed on the door hanger or  re-schedule a yard inspection for potential mosquito sources within 3 business days. You can schedule a yard inspection during regular business hours at 559-732-8606 or toll-free at 877-732-8606. You received this notice because your property is located in a high risk area for invasive Aedes aegypti mosquitoes. This service is free.

I received a white door hanger. What do I need to do?

You do not need to do anything at this time. Technicians have inspected for and/or treated mosquito sources in your front/back yard. Technicians may need to return at a later date to follow up on the mosquito sources. If you would like more information about what technicians found, how to prevent future breeding, or to schedule a re-inspection, call 559-732-8606 or toll-free 877-732-8606 during regular business hours. This service is free.

I received a final notice in the mail. What do I need to do?

You need to schedule a yard inspection for potential mosquito sources. You can schedule a yard inspection during regular business hours at 559-732-8606 or toll-free at 877-732-8606. If you have already scheduled an inspection, please disregard the final notice. If your property has already been inspected, you may need to schedule a re-inspection if mosquito sources were found. Please check your copy of the inspection form for the return date. This service is free. You received a final notice in the mail because you were not present when technicians first tried to make contact at the property and you have not scheduled an inspection at the time the letter was sent.

I received a trap host door hanger. What do I need to do?

You do not need to do anything at this time. This is a notice that mosquito trapping has started for the year, and you, or someone at your residence, has given permission for your front yard to host a weekly trap. If you are no longer interested in being a trap host or have additional questions, you can contact the District during regular business hours, by calling 559-732-8606.

Adult and Larval Mosquito Treatments

Why is the District treating certain areas for adult mosquitoes but not others?

The District uses adult mosquito treatments to reduce the public health risk of mosquito-borne diseases to District residents. The decision to treat certain areas is based on many factors including available staff and equipment, virus detection in mosquito samples and dead birds, the number of human cases, and mosquito abundance.

How are the adult treatments taking place?

Adult mosquito treatments are applied using ultra-low volume (ULV) equipment that is mounted on a truck. This is referred to as ground ULV. Ground ULV is carried out usually in urban areas to control adult mosquitoes. The adulticides are applied at very low dosages. The low dosages, plus natural degradation by UV light and water, ensure minimal risk. The District uses pyrethroid-based products for ground ULV adulticiding. Pyrethroids are a synthetic insecticide, modeled after a botanical insecticide produced primarily from the flowers of Tancetum cinerariifolium, which is a species in the chrysanthemum plant family. These botanical compounds act as the plant’s own insecticide to keep insects away.

I live in an area scheduled for an adult mosquito treatment. Are there any precautions I need to take?

Adult mosquito treatments are applied at very low dosages using products that pose low risks to the public. The low dosages, plus natural degradation by UV light and water, ensure minimal risk. The District recommends that people who want to avoid exposure stay inside or away from the application area during and for 30 minutes after the application.

Is there anything I can do to help reduce the mosquito population?

Yes! Mosquitoes need standing water to lay their eggs and develop into adults. It can take as little as 5-7 days to become an adult mosquito. Dumping any water that lasts for more than 3 days will get rid of mosquitoes before they can become biting adults. Mosquitoes only need a tablespoon of water for their eggs! Delta Mosquito and Vector Control District also offers free mosquitofish for larger water sources such as backyard ponds, water features, and animal water troughs. Yard inspections are available by request for residents who can be present during the inspection so staff can explain habitat types, demonstrate source reduction activities, and share best water management practices.

How do I sign up to be notified by email when adult mosquito treatments take place?

Please contact the District at 559-732-8606 to sign up for treatment notifications.

What is a larval mosquito treatment?

Larval mosquito treatments are used to stop or prevent mosquitoes from developing in a source of standing water.

What types of larval mosquito treatments are there?

There are several types of control methods for mosquito larvae and pupae. These treatments can include Bti, insect growth regulators, surface films, and even mosquito fish. Visit our Control page for more information on types of treatments to control mosquito larvae.

Why do you treat water sources instead of just treating adult mosquitoes?

Typically, reducing and treating sources of standing water that contain developing mosquitoes is more effective than treating adults. Adult mosquitoes can change their location while larvae and pupae are stuck in their water source.

What are Sterile Insect Techniques (SIT)?

Sterile Insect Techniques (SIT) are environmentally-friendly insect control techniques used to control mosquitoes. In SIT, sterile male mosquitoes are released to mate with the local population of females of the same mosquito species. Once the sterile males mate with local females, the resulting eggs will not hatch, reducing the number of female mosquitoes that can spread diseases.

For more information regarding SIT, please read the Mosquito and Vector Control Association of California’s SIT Sheet.

Preventing Mosquito Bites

Why do mosquitoes bite?

Only female mosquitoes bite. Female mosquitoes bite humans and other animals to get a blood meal. They need protein from the blood to make their eggs.

Why are mosquitoes attracted to me?

Mosquitoes rely on a combination of stimuli in order to seek their hosts: carbon dioxide, temperature, moisture, odor, color, and movement. In this case, mosquitoes can be attracted to humans because we produce carbon dioxide when we breathe and also release chemical signals to mosquitoes when we sweat.

How can I prevent mosquito bites?

Use Environmental Protection Agency (EPA)-registered repellents and wear loose long-sleeved shirts, and pants that are light-colored. When using, or purchasing, EPA-registered repellents, look for the active ingredients DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), 2-undecanone, or para-menthane-diol (PMD). Click here for more information about EPA-registered repellents.

Is there anything I can do to help reduce the mosquito population?

Yes! Mosquitoes need standing water to lay their eggs and develop into adults. It can take as little as 5-7 days to become an adult mosquito. Dumping any water that lasts for more than 3 days will get rid of mosquitoes before they can become biting adults. Mosquitoes only need a tablespoon of water for their eggs! Delta Mosquito and Vector Control District also offers free mosquitofish for larger water sources such as backyard ponds, water features, and animal water troughs. Yard inspections are available by request for residents who can be present during the inspection so staff can explain habitat types, demonstrate source reduction activities, and share best water management practices.

How can I keep mosquitoes out of my house?

Mosquitoes can follow you into your home or enter through unscreened doors and windows that have been left open or are opened frequently. Screening your doors and windows is a great solution to prevent mosquitoes from entering homes. Regularly check your screens to make sure they fit tightly into the window or door frame and that there are no holes. Also, make sure you do not have standing water inside your homes. Vases, plant trays, and unused bathrooms are potential breeding sources for the invasive Aedes mosquitoes.

Mosquito Sources

What is a mosquito source or a breeding source?

A mosquito source, also known as breeding source, is water where mosquito eggs, larvae, and pupae live and develop into adults. Any water source that lasts for 3 or more days is a potential mosquito source.

How big of a water source do mosquitoes need?

Mosquitoes can develop in water sources as small as a bottle cap or as large as a marsh. Different mosquito species prefer different water sources.

How long does the water have to sit for mosquitoes to develop?

Most mosquitoes can develop from an egg to an adult in as little as 5-7 days. Some species can develop even quicker. Warmer weather shortens this time frame while colder temperatures increase it.

Why does dumping water or getting rid of standing water get rid of mosquitoes?

Mosquitoes need to lay their eggs on water or at the waterlines of standing water. Without standing water, mosquitoes cannot lay their eggs and the eggs cannot develop into adult mosquitoes. No standing water means no mosquitoes.

How often should I dump standing water?

Potential mosquito sources should be dumped at least once a week. Without water, mosquitoes can’t develop into biting adults. Since it can take as little as 5 to 7 days to develop into an adult, dumping water once a week will prevent most mosquitoes from becoming biting adults.

What should I do if the water source is too large to dump every week or too difficult to drain?

There are several options available depending on the source. The District provides free mosquitofish for larger water sources like ponds, water troughs, and large fountains. Maintaining appropriate chlorination of swimming pools, hot tubs, fountains, and birdbaths will also prevent mosquito breeding.

What should I do if my neighbor has a potential mosquito source?

You can anonymously report potential mosquito sources here or call during regular office hours. We will not share your information.

How do I stop my pond from producing mosquitoes?

The District provides free mosquitofish for ponds, horse troughs, large fountains, and other water sources. If you would like mosquitofish, contact our office at 559-732-8606 or toll-free at 877-732-8606 during regular business hours. Fish and turtles are common types of animals that feed on mosquito larvae. Both small fish and small turtles will feed on mosquito larvae until they reach a certain size where they prefer to eat larger meals. However, mosquitofish will always eat any mosquito larvae because they will not grow more than about 3 inches.

How do I stop my fountain from producing mosquitoes?

Properly maintaining and running the fountain will maintain a constant flow of water and prevent mosquitoes from breeding. Additionally,maintaining chlorination or other appropriate fountain treatment or keeping the fountain completely dry will prevent mosquito breeding. The District also offers free mosquitofish for very large fountains. If you would like mosquitofish, contact our office at 559-732-8606 or through the toll-free number 877-732-8606 during regular business hours.

How do I stop my birdbath from producing mosquitoes?

Empty and clean by scrubbing birdbaths at least every three days.Chlorinating birdbaths can also help prevent mosquito breeding. Invasive Aedes mosquitoes can lay their eggs on the sides of the water in the birdbath and can remain dry, and viable, for up to a year.

How do I stop my pet water bowl or water trough from breeding?

Pet water bowls should be washed every three days to remove potential mosquito eggs. If you have an automatic pet watering bowl, the automatic feature must also be cleaned. Mosquitofish can be placed in troughs to prevent mosquitoes from breeding. If you would like mosquitofish, contact our office at 559-732-8606 or through the toll-free number 877-732-8606 during regular business hours.

Mosquito-Borne Diseases

What are mosquito-borne diseases?

Mosquito-borne diseases are diseases caused by pathogens that are spread through the bite of an infected mosquito. These include malaria, yellow fever, Zika, West Nile virus, St. Louis encephalitis virus, Western equine encephalitis virus, dengue, chikungunya, dog heartworm, and many more.

What mosquito-borne diseases are in the District?

West Nile virus and St. Louis encephalitis virus are detected in the District every year. Currently, the District tests Culex mosquitoes and dead birds for West Nile, St. Louis Encephalitis, and Western Equine Encephalitis viruses.

How does the District know there are mosquito-borne diseases?

The District tests mosquitoes collected within the District border using RNA extraction and reverse transcription real-time polymerase chain reaction (RT-PCR). Dead birds are also tested for mosquito-borne disease.

Can mosquitoes transmit pathogens to my pets and animals?

Mosquitoes can transmit pathogens to pets and animals. The three mosquito-borne diseases found in our district, West Nile, St. Louis encephalitis, and Western equine encephalitis viruses, primarily circulate in birds. West Nile Virus and Western equine encephalitis virus can be transmitted to horses. However, there is a West Nile and Western equine encephalitis virus vaccine available for horses. Additionally, dogs can also be infected with dog heartworm, a mosquito-borne parasite.

Traveling & Mosquitoes

How do I know what vector-borne diseases I should be concerned about when traveling?

Check your destination for health risks at the Center for Disease Control Travelers’ Health website and consult with a travel health practitioner to ensure you receive the appropriate immunizations, preventative treatments, and resources you need for a safe trip. Start planning at least 3 months in advance to ensure that you have time to complete all travel requirements and recommendations.

Do I only need to be concerned about vector-borne diseases when I travel outside the USA?

No! Mosquitoes, ticks, and other vectors are common throughout the USA and its territories. Prevent insect bites anytime you travel by using an EPA-registered insect repellent.

What should I bring to prevent mosquito and tick bites when I travel?

Bring an EPA-registered insect repellent with the active ingredients DEET, picaridin, ID3535, oil of lemon eucalyptus, 2-undecanone, or para-menthane-diol at 20% or above. These repellents come in sprays, wipes, and lotions can easily be transported in your luggage. Consider sleeping under a mosquito net depending on the country you are visiting. Consult with the appropriate travel agency for specific information about what you can bring into the transporting vehicle.

What do I do if I contracted a mosquito-borne disease while traveling?

Contact your physician and local public health department as soon as possible. Prevent mosquito bites by wearing loose, light-colored, long-sleeve shirts and pants and using an EPA-registered insect repellent and reapplying as directed on the product label. Prevent mosquitoes from entering your house by ensuring that all your windows and doors have screens in good condition and by running your air conditioning.

Vectors

What is a vector?

A vector is any animal or insect that is capable of transmitting pathogens to people or harming them. Common vectors around the world are rodents, mosquitoes, ticks, and fleas. In our District, mosquitoes are the primary vectors of public health concern.

Besides mosquitoes, what other vectors should I be concerned about?

In our District, mosquitoes are the primary vectors of public health concern because an infected mosquito can transmit West Nile virus, St. Louis encephalitis virus, or Western Equine Encephalitis virus through their bite. Other vectors, such as ticks are capable of transmitting pathogens but these diseases are relatively rare within the District.

What diseases can ticks transmit?

Within California, ticks have been known to transmit Lyme disease, tularemia, Rocky Mountain Spotted Fever, 364D rickettsiosis, tick-borne relapsing fever, and tick paralysis.

What diseases can fleas transmit?

Within California, fleas have been known to transmit murine typhus and plague.

Can I request service for vectors other than mosquitoes?

You can contact the District during regular hours at 559-732-8606 or toll-free at 877-732-8606 for more information.

Mosquito Species

Which native mosquito species are found in the District?

There are about 14 native mosquito species within the District that are considered to be of public health concern because of their nuisance biting or potential to transmit pathogens through their bite. To learn more about mosquitoes and the species found in the District, visit our vector page.

What pathogens can native mosquito species transmit?

Within the District, three Culex mosquito species are capable of transmitting West Nile virus, St. Louis Encephalitis virus, and Western Equine Encephalitis virus.

Where do native mosquito species lay their eggs and develop into adults?

All mosquito species need water to develop into adults. The preferred water source can vary widely from seemingly clean water to foul, stagnant water. The size of the water source can also vary, from small puddles to green swimming pools and ponds. For more detailed information, please visit our vector page.

What is an invasive mosquito species?

An invasive mosquito species is one that has been introduced to the region recently. It is not part of the natural ecosystem.

What kind of invasive mosquito species are found in the District?

Currently, the only invasive mosquito in the District is Aedes aegypti, also known as the yellow fever mosquito. For more information, please visit our vector page.

Where can I find invasive mosquito species?

Aedes aegypti mosquitoes prefer to live near people where they have easy access to their preferred food source (humans) and to standing water in man-made containers.

What diseases can the invasive Aedes aegypti transmit?

Once infected, Aedes aegypti are capable of transmitting zika, dengue, chikungunya, and yellow fever virus through their bite.

Service Request? Get in Touch.

Contact

1737 West Houston Ave
Visalia, CA. 93291
Ph. 559-732-8606
TF. 877-732-8606
Fax. 559-732-7441

Hours

Monday–Friday,
7:30 AM to 4 PM (excluding holidays)