Frequently Asked Questions

• What if I don't want my property treated or sprayed?
• Are mosquitoes attracted to some people more than others?
• What purposes do mosquitoes serve?
• What diseases do mosquitoes carry?
• Do mosquitoes carry AIDS?
• Are the chemicals harmful to people or pets?
• Will DEET hurt children?
• What is the best personal repellent?
• How can one type of insect be controlled without hurting other insects or wildlife?
• What is the best way to control mosquitoes?
• How effective is the spray?
• Why can't mosquito control programs spray during the day?
• How do Districts decide where to spray?
• How long does the mosquito spray last?
• What does Mosquito Control do and why?
• How safe are the pesticides being used?
• When do you spray?
• Is it true that only certain mosquitoes bite and/or transmit disease?
• Can I as a homeowner make a difference in the mosquito population in my area?
• Can I spray my yard myself?
• Why is it so important that I inspect my yard when ditches and woodland surround me

Q. What if I don’t want my property treated or sprayed?

A. Call Chesapeake Mosquito Control at 757-382-3450 so that we can mark your property for no spray. Also, please visit Chesapeake Alert to register for Chesapeake Alerts and receive automatic notification of night time spray in your area.

Q. Are mosquitoes attracted to some people more than others?

A. Yes. Mosquito attraction to humans is a very complex matter. Primarily, mosquitoes are attracted to the carbon dioxide (CO2) emitted from the breath and to the chemicals produced by the skin. In addition to CO2,some species of mosquitoes are attracted to certain fragrances and colors. During mosquito season it is recommended that people who wish to be less attractive to mosquitoes wear unscented products (hair spray, soap, deodorant, etc.) and light colored, loose-fitting clothing.

Another way to become less attractive to human biting mosquitoes is to wear commercially available, proven mosquito repellents. The most common proven repellent is DEET (N,-diethyl-meta-toluamide). There are many unproven products commercially available as mosquito repellents. No matter what repellent is used, the entire label should be read thoroughly.

Q. What purposes do mosquitoes serve?

A. All species of plants and animals have their place in nature. Mosquitoes are no exception. They are an important link in the food chain. Many animals depend on them as a source of food. During their aquatic stage, mosquito larvae provide food for the other aquatic insects such as, dragonfly nymphs and beetles, fish, frogs and other water-dwelling animals. As adults, mosquitoes are eaten by birds, bats, spiders, lizards and other insects. Mosquitoes do not feed on blood alone. The blood meal is taken by the female to produce eggs. Both male and females need liquid nourishment for food. Plants provide the source of liquid nourishment. Mosquitoes feed on plant nectar, honeydew, fruit juices and liquids oozing from injured plants. Because of this need for nourishment, mosquitoes are important pollinators of wildflowers during this feeding process.

Q. What diseases do mosquitoes carry?

A. Mosquitoes kill more than one million people each year with the deadly diseases they transmit. These diseases include malaria, filariasis, dengue fever, yellow fever and viruses that can cause encephalitis, or swelling of the brain, such as Eastern Equine Encephalitis virus (EEE) and West Nile virus (WNV). Mosquitoes can also vector (transmit) dog heartworm. It is important to note that not all mosquitoes carry diseases. Each of the diseases is mainly transmitted by only a few species of mosquito. Malaria is a single-celled parasite (Plasmodium spp.) that is transmitted by the bite of an infected Anopheles mosquito. An infected person feels tired, has muscle pain, headaches and loss of appetite, much like the onset of flu symptoms. This is followed by chills and high fever which usually reoccur every few days. Lab tests are required to confirm malaria infection. Yellow fever, (so named because the infected person turns yellow from jaundice) is caused by a virus that is carried by an infected mosquito. Encephalitis is difficult to determine because laboratory confirmation is required, a costly and time consuming procedure. Mosquito control surveillance programs gather data from wild birds and sentinel chicken flocks to determine the presence of encephalitis antibodies. Prevention and control of encephalitis has historically been addressed by local mosquito control programs.

Dog heartworm is caused by juvenile worms (called microfilariae) leaving the mosquito's proboscis and being deposited on the skin of a dog while the mosquito is taking a blood meal. These microfilariae find the puncture wound made by the mosquito and crawl into the dog's bloodstream. Heartworm is a serious problem which can lead to death for dogs. However, veterinarians can prescribe medication to prevent heartworm.

Q. Do mosquitoes carry AIDS?

A. No. No evidence to support that likelihood exists. If HIV infected blood is taken by a mosquito the virus is digested (killed) inside the body of the mosquito. If a mosquito takes a partial HIV infected blood meal from a person and then immediately feeds on an uninfected person, there would not be enough HIV particles present to transmit the disease. In fact, it is highly unlikely (1 in 10 million chance) there would even be a single unit of HIV present. Finally, for a mosquito to be able to carry AIDS, the disease would need to pass from the gut of the mosquito to the salivary glands where it would later be injected into the next host. This is quite a long and extensive process even with diseases that can be transmitted by mosquitoes (like encephalitis).

Q. Are the chemicals harmful to people or pets?

A. Any chemical, even salt or caffeine, in a large enough dose can be harmful. The amounts of mosquito control chemicals that come out of the mosquito trucks and aircraft are not harmful to humans or pets. As with any chemical, it is always a good idea to keep exposure to a minimum. For this reason, children should not be allowed to follow the mosquito trucks as people often did in the 1940s and 1950s. Pets usually are repelled by the high pitch of the machine. It can be difficult to see or smell the insecticide coming out of the truck or plane. Therefore, even if it seems that they are not spraying, the trucks should not be followed. A person or pet that accidentally gets hit with the spray may feel a momentary slight burning or stinging sensation on the skin or in the eyes and may cough briefly if they inhale the spray. The smell is usually worse than the taste or sting. Unless someone is very sensitive or allergic to chemicals, washing the skin with water is all that is needed. At the low insecticide dosage used, no other symptoms should be experienced. If other symptoms are experienced, a physician should be consulted immediately. If appropriate: People who are chemically sensitive should give their names to their local mosquito control program so they can be notified prior to any spraying.

Q. Will DEET hurt children?

A. DEET can irritate eyes and sensitive skin or dry it out. Some people are allergic to DEET. Infants and children tend to be more sensitive to DEET than adults. To minimize adverse reactions to DEET:

• apply repellent sparingly and only to exposed skin
• apply repellent to clothing to reduce DEET absorption through the skin
• avoid using products with DEET concentrations over 30% (particularly on children and infants)
• avoid inhalation or ingestion of repellents, contact with eyes, wounds or irritated skin
• avoid applying repellents to portions of children's hands which are Rely to come into contact with their eyes or mouth

While DEET is an effective repellent, high concentrations can feel unpleasantly oily and can melt plastic, watch crystals and paint finishes. It is safe on nylon, cotton and wool. However it can damage rayon, acetate and spandex. Test repellents on an inside seem of polyester/cotton blends to see if DEET damages them. Products with citronella, an oil extract from lemon scented grass or from eucalyptus, can be purchased from health food or camping stores. Avon Skin-So-Soft is widely used as a repellent, but it is not effective for all people. These products must be reapplied more frequently, and they are much less effective than DEET

Q. What is the best personal repellent?

A. It has long been known that the most effective repellents are those which contain DEET. DEET is the abbreviation for the chemical N,N-diethyl-meta-toluarnide. DEET has been sold in the United States since 1956 and is used by 50-100 million people each year. It repels mosquitoes, no-see-ums, fleas, ticks, gnats, horse flies, deer flies, yellow flies and chiggers. Repellents containing DEET are available as pump sprays,aerosols, lotions, creams, soaps and sticks. In general, the inexpensive products contain less than 10% DEET, while the more expensive ones are at least 20%DEET. There are over 40 products containing from 5% to 95% DEET which can be purchased. Products with more than 35% DEET are available, most often, through camping and outdoor supply stores. If a little DEET is good, is a lot of DEET better? Not necessarily. In tests done by the army, repellents with 30-40%DEET worked twice as well as repellents with 75% DEET. Read the label and check to see what percentage of the product is DEET. This information is found underactive ingredients. The label may say DEET, or it may spell out the chemical name. Some people need to use higher concentrations, while a lesser concentration may suffice for others. It is always best to use the lowest concentration that is effective. People should check to see if it is a controlled release formula (long lasting) and compare the amount of product and the type of application. Lotions provide the most even coverage. Sprays are more convenient but require greater care in applying. The entire label should be read before choosing what is best for a family.

Q. How can one type of insect be controlled without hurting other insects or wildlife?

A. There are three important factors which allow mosquito control applicators to target mosquitoes, while having a minimal effect on other organisms. These include the way insecticides kill, the amount of insecticide sprayed and the time the insecticide is sprayed. First, modern pesticides have become more specific as to what they will affect when used in the correct amounts. For example, pesticides which kill only insects, affect parts of the insect that other animals and plants do not possess. Just as rat poison, when used in the proper amount, does not kill insects and weed killer does not kill birds, mosquito pesticides, when used in the proper amounts, do not kill birds or rats. Most of the pesticides used to kill mosquito larvae have minimal effects on other organisms. Second, the amount of pesticide, or dose, is an important factor. The pesticides that are used to kill adult mosquitoes can, and do kill certain other insects, particularly those that are similar to mosquitoes, such as blind mosquitoes, no-see-ums (biting midges) and other small insects. They do not kill larger insects like house flies, butterflies, horse flies or beetles because the dose applied is not high enough. Third, while some insecticides used to kill adult mosquitoes can kill bees, they are not used during the day when bees, and many other insects, are flying around. They are used at dusk or at night when the mosquitoes are flying and the bees are not. That's one reason trucks do not spray during the day.

Q. What is the best way to control mosquitoes?

A. The best way is to eliminate the water in which they breed. Backyards should be checked for containers, even very small ones that hold water. Pet dishes, tin cans, flower pot holders, plugged gutters, tires, birdbaths, kiddy pools, toys, bromeliads, anything that can hold water should be checked. Water should be dumped every third day if the source is not eliminated. Those containers that are too large to turn over should be covered. While it is possible to drain larger wet areas or flood them so mosquitoes can not breed, those methods are generally not good for wildlife. Sometimes it is possible to add fish which eat mosquito larvae to the pond. The next best method is to control mosquitoes by treating the water with insecticides that kill only mosquitoes. Unfortunately, there is no way to stop mosquitoes from mating and, although bats, birds, other insects and vertebrates eat mosquito larvae, they do not control mosquitoes to the level people want or that will prevent disease transmission.

Q. How effective is the spray?

A. Pesticides properly applied to water kill 95%-100% of the mosquito larvae and, thus, are very effective. It is more difficult to tell how effective sprays to kill adult mosquitoes are, because it is not known exactly how many mosquitoes are present before spraying. Adult sprays applied by aircraft are very effective because the spray covers a very large area, usually several square miles. Reductions of 90% are common. Adult sprays applied by trucks can be just as effective where parallel roads are close together, where there is a light wind and the vegetation around houses is not thick. It is less effective if there is no wind, high humidity, too few roads and heavy vegetation. Traps are often used to measure the population levels before and after spraying

Q. Why can't mosquito control programs spray during the day?

A. It is not effective to spray during the day for several reasons. The primary reason is that the spray would be lifted away from the ground very quickly by the rising air currents that occur during hot days. At dusk and at night, the insecticide stays near the ground. The second reason is that most mosquitoes that bite during the day (Asian tiger mosquito) are breeding in containers or plants in the yard and are better controlled by eliminating the water in which they grow. Mosquito problems can be reduced by checking yards for containers, even very small ones that hold water. People should look for pet dishes, tin cans, flower pot holders, plugged gutters, tires, bird baths, kiddy pools, toys, bromeliads, trash cans, etc. Water should be dumped every third day if the source is not eliminated. Containers that are too large to turn over should be covered. Daytime spraying is not practiced to avoid killing beneficial insects, particularly bees; to reduce people's and wildlife's exposure to the pesticide; and to eliminate the potential traffic hazard of a slow-moving vehicle during high traffic volume times. The mosquito control vehicle's slow-moving, flashing light and unique sound is easily seen and identified at night.

Q. How do districts decide where to spray?

A. Where to spray is determined by trapping adult mosquitoes, observations by mosquito control workers or by citizen complaints.

Q. How long does the mosquito spray last?

A. Adult mosquito sprays are effective for only 24 hours or less. Spraying an area does not prevent mosquitoes from re-entering the area.

Q. What does Mosquito Control do and why?

A. Mosquito control districts attempt to safely and economically control mosquitoes to a safe and tolerable level reducing the risk of mosquito borne disease and the nuisance level to acceptable/safe conditions. The primary focus is on reducing the viral risk and the operational emphasis is on habitat reduction/elimination and larval control. The ultra low volume (ULV) spraying is used as needed for the control of adult mosquitoes.

Q. How safe are the pesticides being used?

A. The primary pesticides used in the larval control operations have very low human/mammalian toxicity and most are very environmentally friendly. Most are biological agents that have bacteria as the active ingredient and are very specific to mosquitoes while in the larval stage. Minnows are often used when feasible as a natural control. The pesticides used to control the adult mosquitoes also have very low human/mammalian toxicity and have been used and tested many years. Most are "synthetic pyrethroids" which is man made to work like a natural product made from exotic chrysanthemum plants. Some are also natural pyrethrums and actually made from the plants. This is where some people may have an allergic reaction if they are allergic to these type plants. These people may contact their local mosquito control district and ask to be place on a "contact list" to be contacted when spray operations are planned or call the spraying hotline to find out when spraying is scheduled and where. Even though these same pesticides are used in the agricultural market for pest control on plants they are applied in the public health industry ata much lower application rate and are widely used in home pest control products. These products have very limited residual and biodegrade rapidly in the environment. They have very low human/mammalian toxicity. A good part of the odor and taste that might be experienced is from the mineral oil that is used as a diluent. There is currently much research and work being done with aqueous materials that can eliminate or at least greatly reduce the use of these oils.

Q. When do you spray?

A. Several years ago it was an accepted practice for control districts to spray as a routine, meaning the trucks would be in a certain area on a given day on a weekly basis. Spraying in the evening and early morning hours, the most effective time for most species, is normally done on an as needed basis. When surveillance data indicates that the mosquito populations are great enough to warrant the spraying to lessen the risk of disease and reduce the annoyance factor for outside activities. With the extensive research and development of safer more environmentally sensitive and more selective larvicides, the need for "fogging" or Adulticiding has decreased and control efforts have focused more on controlling mosquitoes before they become adults and begin biting. However in an area like Chesapeake, our proximity to saltwater marshes and swamps such as the Great Dismal Swamp significantly reduces the effectiveness of Larviciding against some species. The homeowner can play a very important role in reducing some of our most problematic species, which breed in artificial containers and tend to stay near humans. Our control efforts, though an important part of, are limited in controlling these species. Especially the "tiger" mosquito!

Q. Is it true that only certain mosquitoes bite and/or transmit disease?

A. Yes. Only the female mosquito bites. The male feeds on plant juices to be used to fertilize the eggs of the female, which must then have a blood meal before she can produce viable eggs. Some species of mosquitoes only bite birds, some cold-blooded animals and some prefer rodents and etc. Not all are capable of transmitting disease. Some are capable of transmitting several viruses and some are only capable of transmitting one virus. The virus must undergo certain metabolic actions within the mosquito before it can then be transmitted via the bite. Some viruses are not capable of undergoing this and some are not present in sufficient quantity in the mosquito to be transmitted. Some mosquito species don't bite at all.

Q. Can I as a homeowner make a difference in the mosquito population in my area?

A. YES! There are certain mosquito species that tend to breed in artificial containers, tires, tree holes and such and tend to stay close to humans, and with a ready blood meal available doesn't need to leave the area to complete the process of repopulating frequently. Even small quantities of water can provide ample breeding opportunity for these species. A plastic bottle cap can be the home to several mosquito larvae. Some species are more apt to breed in natural environments such as ditches, swamps and low areas. These are more difficult for the homeowner to control and only physical means such as screens, long sleeves repellents and such may be the only defenses in the absence of an effective mosquito control program.

Q. Can I spray my yard myself?

A. Yes. If you observe adult mosquitoes in your yard, you can use any one of several aerosol preparations which are available at stores. If the label states the product is effective for killing adult mosquitoes outdoors, it should be effective. These preparations are safe if you follow the directions on the label. Emphasis should be placed on basic yard sanitation and reducing breeding grounds, not spraying chemicals.

Q. Why is it so important that I inspect my yard when ditches and woodland surround me?

A. Throughout the world there are over 3,000 species of mosquitoes. In Virginia there have been 55 species of mosquitoes identified, of those we will typically deal with 15 - 20 in a season. Some of these species are very important in the disease transmission cycle, some are less important and some not at all. Of the ones that are important some are the species of mosquito that breeds in containers and prefer to remain near these sites that are sometimes found in our own backyards. Such as old tires, buckets, boats, house gutters, tarps, toys and etc. As mentioned above a bottle cap full of water can provide the habitat for several mosquitoes that will then lay their eggs in the same spot and produce more,a continuing cycle (every 7 -10 days) The ditches and woodlands produce different species, that again can be important vectors or not so important. In normal conditions mosquito control districts can control these areas if they're aware of the standing water and have access to the same. In addition the trucks are more effective with these species as they may travel a distance in search of a blood meal.

For more information or assistance call your local Chesapeake Mosquito Control Commission:

Main Office 382-3450
SPRAYING HOTLINE 382-3456