- How many kinds of mosquitoes are in Clark County?
- Why do mosquitoes bite?
- Why do mosquito bites welt?
- Why do some people get more mosquito bites than others?
- What steps can I take to avoid mosquito bites?
- Do mosquitoes carry diseases?
- Can mosquitoes transmit AIDS?
- How do mosquitoes grow?
- How long do mosquitoes live?
- Why are there no mosquitoes in winter?
- Why do mosquitoes breed only in certain areas?
- Why should mosquito activity be controlled?
- What is IPM?
- What kinds of insecticides are used to control mosquitoes, and how?
- Is treating with insecticides dangerous to humans?
- What are alternative methods to control mosquitoes?
- Where can I get mosquito-eating fish for my pond?
- Do electronic repellers and bug zappers really control mosquitoes?
- If I build bat (or bird) houses, will I eliminate my mosquito problem?
- What should I do if I find a mosquito nest in my tree or shrubs?
- Can the mosquito crew come and spray my home?
- Can the crew do something to get rid of midges (or lice, rats, bats, wasps) in my neighborhood?
1. How many kinds of mosquitoes are in Clark County?
The mosquito control field crew has identified 14 different varieties in Clark County the past five years. Actually, there are about 3,000 different species of mosquitoes worldwide. These 3000 species are divided among 28 different genera. The genus Aedes are some of the worst pests; we have a substantial amount of these mosquitoes most years.
Genera found in Clark County in the past several years have such exotic names as Aedes, Ochlerotatus, Culex, Anopheles, Culiseta and Coquillettidia. In addition, each of these classifications contains variations of mosquito breeds, each with its own name.
Mosquitoes have successfully adapted to climates from arctic to tropical, and have developed means of locating blood-carrying hosts in each locale. Some mosquitoes prefer to feed on frogs, some on birds, others on mammals. No single mosquito repellent product works equally well on all mosquitoes; but for the mosquitoes found in this area, products containing DEET are most effective.
2. Why do mosquitoes bite?
Mosquitoes require blood to develop fertile eggs. Males do not lay eggs, and do not bite. Females are the egg-layers; they seek "hosts" that will give them a blood meal. Females lay multiple batches of eggs, and require a blood meal for each batch they lay.
Mosquitoes rely on sugar as their main source of energy. Both males and females feed on plant nectar and fruit juices. Sugar is burned as fuel for flight, and must be replenished daily. Blood is reserved for egg production and is sought less frequently.
People are not the primary target for blood hosts for mosquitoes. Even mosquitoes that carry encephalitis seem to prefer bird hosts. Mosquitoes bite people when they get the chance, but they are better able to track the scent of animals most abundant in their habitat.
3. Why do mosquito bites welt?
When the female mosquito pierces the skin with her mouthparts, she injects a tiny amount of saliva into the wound before drawing blood. The welt that appears after a mosquito bite is not a reaction to the wound, but an allergic reaction to the saliva injected during the bite.
In most cases, itching and swelling subsides within several hours. In some highly sensitive people, they may persist for several days. Scratching mosquito bites can result in infection if bacteria under fingernails are transferred to the wounds.
4. Why do some people get more mosquito bites than others?
Female mosquitoes use the carbon dioxide we exhale when we breathe as a primary clue to our location. From 100 feet (30 meters), mosquitoes can smell human scent, especially the carbon dioxide. They follow the scent upwind and can see people at about 30 feet (10 meters). They don't see very well; at 30 feet they have trouble distinguishing people from other objects of similar size and shape, such as tree stumps, large containers, etc. When they get within 10 feet, they can sense body heat. They use thermal receptors on the tip of their antennae to locate places to bite where blood is near the surface of the skin. The receptor range increases threefold when the humidity is high.
Once the mosquito lands, it uses a number of short-range attractants to determine if it can get an acceptable meal. Folic acid is a chemical that appears to be particularly important. Fragrances from hair spray, perfumes, deodorants and soaps can cover chemical cues, to either attract or repel the mosquito. Dark colors capture heat and make most people more attractive to mosquitoes; light colors refract heat and are generally less attractive. Detergents, fabric softeners, perfumes and body odor can counteract the effects of color.
Generally, there are too many possible factors to predict why one person may be more attractive than another.
5. What steps can I take to avoid mosquito bites?
- Try to avoid times or areas where mosquitoes are most active: near marshes, wet woods, or other swampy locations. (But many mosquitoes are long-distance fliers, and will come into populated areas to find you).
- If possible, stay indoors during peak mosquito activity; for many species at dusk, during the evening or night, and into early morning.
- Keep door and window screens in good repair.
- If it is not too hot or uncomfortable, wear long-sleeve shirts and pants when outside.
- Wear light-colored clothing (in particular, avoid red).
- Avoid outside activities requiring a lot of exertion and generating much carbon dioxide, a natural mosquito attractant. Physical exercise also produces body heat and sweat, which also attract mosquitoes.
- Do not use strong smelling perfumes or cologne, nor fragranced soaps, shampoos or hair spray.
- Use an over-the-counter chemical repellent product that contains the chemical DEET.
- A very small percentage of people may have adverse health reactions to high concentrations of DEET. As a general rule, adults should use repellents containing a 30% concentration or less; concentration for children should be 10% or less. Do not use DEET on infants younger than two years old.
- It is better to apply a product having a lesser concentration of DEET more frequently than one with a higher concentration less often.
- Be sure to follow all label instructions for application of any repellent.
- Practice good water sanitation around your home to control mosquito breeding.
6. Do mosquitoes carry diseases?
Any insect that feeds on blood can transmit disease organisms from human to human, but mosquitoes are the most formidable transmitters of disease in the animal kingdom. Mosquito-borne diseases are caused by human parasites that enters their blood stream. The female mosquito picks up the parasite when she sucks blood to develop her eggs. The parasites complete a portion of their own life cycles in the mosquito, and either multiply, change in form inside the mosquito, or do both. After she lays her eggs, the mosquito seeks a second blood meal and transmits the fully developed parasites to the next host.
Some diseases mosquitoes spread in people are malaria, encephalitis, and dengue fever. They also can transmit parasites such as heartworm to pets.
7. Can mosquitoes transmit AIDS?
The HIV virus that produces AIDS in humans does not develop in mosquitoes. If a mosquitoes takes in HIV infected blood, the virus is treated as food and digested along with the blood. If a mosquito draws blood from an HIV positive person and then bites a non-infected person, insufficient particles are transferred to cause a new infection.
If a mosquito fully engorged with HIV positive blood is squashed on the skin, not enough virus would be transferred to produce infection. Viral diseases that are transferred by insects produce tremendously high levels of parasites in human blood. Levels of HIV that circulate in human blood are very low.
8. How do mosquitoes grow?
Mosquitoes grow through three stages to adulthood: egg, larvae and pupae. Each species goes through its own set of conditions to complete the process. Some species lay eggs on damp soil that can remain for years before hatching. Some species need vegetation to complete the cycle. Others need saltwater to develop.
One fact common to all mosquitoes is that stagnant water is needed for development. By removing, covering or draining water-collecting containers, you can disrupt the process and reduce or eliminate mosquito annoyance and potential disease transmission.
9. How long do mosquitoes live?
The normal adult life span is about two to three weeks. The vast majority do not live out the natural span; they are eaten by birds, other insects and spiders, or are killed by wind, rain or drought.
10. Why are there no mosquitoes in winter?
Mosquitoes, like most insects, are cold-blooded animals. They cannot regulate body heat; their temperature is essentially the same as their surroundings. Mosquitoes are most comfortable at about 80°F. They become lethargic at 60°F, and cannot function at all below 50°F. In tropical areas, mosquitoes are active all year.
In temperate climates, adults become inactive at the onset of cool weather and hibernate through the winter. Some kinds hibernate as embryos in eggs laid by the last generation of females in late summer. The eggs hatch in spring when water temperature rises. Other varieties over winter as adult females that mate in the fall, hibernating in burrows or hollow logs or basements, and emerge in the spring to lay eggs that produce the next generation. A limited number of mosquitoes over winter as larvae, often buried in mud of freshwater lakes and rivers. When temperatures rise in the spring, they begin feeding, complete their growth and emerge as adults.
11. Why do mosquitoes breed only in certain areas?
Mosquitoes breed in standing water. Eliminating sources of stagnant water on your property reduces risk of mosquito nuisance. Rain gutters, old tires, stagnant fish ponds, open trash receptacles, tarp-covered wood piles that pool stagnant water are breeding sites. But, though you may take steps to clean up your property, your neighbor's actions or inaction, or nearby wetland areas near your home may make subject you to mosquito problems.
12. Why should mosquito activity be controlled?
- Mosquitoes can carry numerous viruses and bacterium, some fatal to humans.
- Mosquitoes have spread disease through entire populations, altering the history of mankind. It is estimated that mosquitoes have killed more human beings than all wars, famines and natural diseases combined - more humans than are alive today.
- Controlling mosquitoes can eliminate or greatly reduce instance of endemic diseases.
13. What is IPM?
Clark County Mosquito Control District follows an Integrated Pest Management (IPM) program. IPM does not mean that no pesticides can be sued (as is sometimes misunderstood), nor that using insecticides is a minor part of the mosquito control strategy. IPM is a program that
- makes best use of a combination of the most practicable control methods
- deals with real-world situations
- treats mosquito problems only when and where they occur
- treats mosquitoes in the most effective, environmentally-compatible and cost effective manner possible
14. What kinds of insecticides are used to control mosquitoes, and how?
There are two basic types - larvicides to control larval or immature mosquitoes, and adulticides for selectively controlling flying or resting adults in areas where adults on-wing are causing problems. All insecticides used in Clark County are registered and approved by the US Environmental Protection Agency (EPA) for specific types of application.
Treatment may be applied by truck-mounted pumping, or in small areas or contained habitats on foot, using backpacks or hand-held applicators. Large areas may be treated aerially by helicopter. The type of treatment is determined by the species to be controlled, the life stages targeted, and the type of habitat or area where treatment will occur.
15. Is treating with insecticides dangerous to humans?
Clark County Mosquito Control District only uses insecticides registered by the US Environmental Protection Agency for mosquito control use. The EPA has determined by science-based testing and review that when these insecticides are applied according to EPA-approved label instructions, application "poses no unacceptable risks to human health, wildlife or the environment." The EPA review process typically involves a pesticide manufacturer spending almost 10 years and many millions of dollars in testing before being allowed to bring a new product onto the market, and must invest significant additional resources to keep existing pesticides re-registered for continued use; all this activity is given careful EPA scrutiny and review.
The products used for mosquito treatment has a very low toxicity to mammals, including humans, dogs, cats, as well as birds and other organisms. Instance of acute toxicity is very low compared to common substances people are routinely exposed to, such as caffeine and nicotine, and even many over-the-counter medications.
The mosquito control program is very targeted and limited to treating mosquito problems only where and when they occur. In almost all cases, larviciding is the primary treatment, because it involves less direct exposure of people to insecticides than adulticides, and is far more effective. Adulticiding is done only as a last resort.
All Clark County Mosquito Control District crew members are certified pesticide applicators, and attend re-certification training classes annually, in addition to receiving other pesticide and mosquito control education and training.
16. What are alternative methods to control mosquitoes?
The most practical alternative to insecticides are collective control methods for source reduction, which uses various approaches to reduce or eliminate breeding habitats and control mosquitoes in the larval stage. People who practice good water sanitation around home or places of business are practicing a form of source reduction. Water management efforts for multiple environmental goals and objectives, such as flood prevention, storm water management, waterfowl production and habitat, fish nursery areas, etc. can be indirect source reduction methods. In some jurisdictions, although not in Clark County at this time, mosquito-eating (Gambusia) fish are stocked in freshwater mosquito breeding habitats or available to the general public for use in home ponds.
17. Where can I get mosquito-eating fish for my pond?
Gambusia are classified as a non-native, not allowed species, and are currently not legal for distribution in Washington state. An alternative is to stock ponds with goldfish, which also eat mosquitoes, although not as quickly as Gambusia. Mosquito "dunks," that float of the surface of water and are impregnated with a pesticide that kills mosquito larvae, are available for purchase at garden and farm supply stores.
18. Do electronic repellers and bug zappers really control mosquitoes?
No. They are not effective, and can actually reduce populations of beneficial insects.
19. If I build bat (or bird) houses, will I eliminate my mosquito problem?
Probably not. Birds and bats may consume mosquitoes, but not enough to make a difference. They prefer larger prey, and will not reduce the mosquito population significantly.
20. What should I do if I find a mosquito nest in my tree or shrubs?
Mosquitoes do not nest. Such nests are probably tent caterpillars. Mosquitoes may rest in cool, shady vegetation, but cannot develop there. Stagnant water is required for the first three stages of life.
21. Can the mosquito crew come and spray my home?
No. The crew does not apply treatment by spraying; fogging of adulticides may be done rarely, but not at individual homes. Because of legal restrictions, the mosquito control district cannot spray or fog neighborhoods or private residences.
22. Can the crew do something to get rid of midges (or lice, rats, bats, wasps) in my neighborhood?
Unfortunately, no. By state statute,the mosquito control district is charged with, funded for, and only authorized to take action to control mosquitoes.
