Pests Attacking Man
Culex tarsalis
Mosquitoes-the Prolific Pests
The unpleasant "hum" of a mosquito is often the first clue that a problem exists in your neighborhood. Large numbers of mosquitoes can thrive in a relatively small quantity of stagnant water as long as it contains enough food material. In the Los Angeles area, a six-acre lake was found to be producing about 500,000 mosquitoes per day! Mosquito Abatement Districts have been established throughout California since 1915, but they only look for major sources to treat. Southern California, with its widespread irrigation, has provided a great habitat for the pesky mosquito providing numerous smaller breeding areas, often right in your own yard!
There are about 200 species of mosquitoes in the United States, all of which live in specific habitats, exhibit unique behaviors and bite many types of animals. California alone is host to about 53 different species of mosquitoes, of which 14 are considered serious pests. Most are known to suck the blood of man. The big four mosquito pests in the southern portion of our state are:
1) Southern House Mosquito (Culex quinquefasciatus) which breeds in foul water and, as the name suggests, is commonly found inside your house. It readily bites man, and is a significant carrier of the encephalitis virus.
2) Encephalitis Mosquito (Culex tarsalis) which can breed in just about any water and is a common carrier of many serious viruses and diseases, especially the West Nile virus. It rests in trees where it bites birds. It also feeds on human blood.
3) Foul Water Mosquito (Culex peus) which breeds in polluted water and frequently carries viruses and diseases, but rarely bites humans.
4) Tule Mosquito (Culex erythrothorax) which breeds in all kinds of shallow ponds, especially marshes. It readily bites people, and is a carrier of viruses and diseases.
Mosquitoes and the Diseases They Can Carry
Almost everyone has had the bad experience of being bitten by a mosquito. Mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva --this is what causes the familiar red bump and itching. They can be voracious feeders--a mosquito can show a weight gain of up to 140% with a single meal of blood. But mosquitoes are more than just blood-sucking pests. A far more serious consequence of some mosquito bites can be the transmission of certain infectious diseases such as malaria, the West Nile virus, yellow fever, filariasis, dengue fever, and several forms of encephalitis. With the establishment of Mosquito Abatement Districts the endemic malaria problem has been eliminated, but with malaria still being a serious worldwide problem, human hosts can bring it into our country where it has still spread in small areas before being detected and treated.
Over the past few years the mosquito-borne West Nile virus has been carried into California from the eastern United States, where it was first detected in 1999. The virus can cause fever and severe headaches, and may cause serious illness in people over 50 years of age, including swelling of the brain and spinal cord. Between 1999-2002 there were 4,305 cases in the United States, with 302 deaths. During 2003 alone there were 9,388 cases with 246 deaths-so the problem is growing. The Center for Disease Control reports that the West Nile virus is permanently established in North America.
Not only can mosquitoes carry diseases that afflict humans, they are also able to transmit several diseases and parasites which affect domesticated animals such as dogs and horses. These include heartworms in dogs and the Western Equine Encephalitis that can be very serious to horses. In 2002, the West Nile virus infected over 14,000 horses with a 40% mortality rate, but fortunately for California all cases were found to the east of the Rocky Mountains.
Mosquito Life Cycle
All mosquitoes share some common traits such as a four-stage life cycle. Most females need to obtain a blood meal before they can produce eggs. After the female mosquito obtains the blood meal, depending on species, she lays her eggs directly on the surface of stagnant water, or in a depression, or on the edge of a container where rainwater may collect and flood the eggs. The eggs hatch and a mosquito larva emerges. The larva/instar lives in the water, feeds on microscopic organisms, and then develops into the third stage of the life cycle called a pupa. The pupa also lives in the water, but no longer feeds. Finally, the mosquito emerges from both the pupal case and the water as a fully developed adult, ready to bite. Only the female bites-and like the male she usually goes after a meal of plant nectar, saps, fruit juices, or insect secretions unless she is ready to breed.
The egg, larva/instar and pupal stages depend on temperature and species characteristics to determine how long they take for development. For instance, Culex tarsalis, one of the common California mosquitoes, might go through its life cycle in 14 days at 70º F and take only 10 days at 80º F. On the other hand, some species have naturally adapted to go through their entire life cycle in as little as four days or as long as one month. Some even migrate to find locations to over-winter and remain basically dormant until the spring unless unusually warm weather occurs.
The type of standing water in which the mosquito chooses to lay her eggs also depends upon the species. The presence of beneficial predators such as fish and dragonfly nymphs in ponds, lakes and streams usually keep most bodies of water relatively free of mosquito larvae. However, portions of marshes, swamps, clogged ditches and temporary pools and puddles may all become prolific mosquito breeding sites. The presence of algae is a good indicator of the mosquito potential. Other sites in which some species lay their eggs include tree holes and containers such as old tires, buckets, toys, potted plant trays or saucers, and plastic covers or tarpaulins. Some of the most annoying and potentially dangerous mosquito species come from these sites, which are particularly hard to eliminate.
Mosquito Characteristics and Facts
Mosquitoes find their hosts by the use of antennae and NOT by sight. They are attracted to moisture, warmth, and carbon dioxide-exactly what you exhale, which frequently leads them to you as you sleep. They are excellent fliers, with some species showing a range of 18-110 miles in the extreme. The average mosquito will fly upwind no more than about two miles and downwind up to nine miles. Most mosquitoes will stay within a three-mile range, flying between five and fifty feet off the ground. They prefer light winds with velocities of below six MPH.
When mosquitoes are outdoors, they seek shelter from the hot sun-a shady harborage area, usually under trees and shrubs. When we have already sprayed those trees and shrubs, the mosquitoes that land there will eventually die. However, in the heat of the summer, when we can't spray those areas (so that your plants are not stressed), you will need to thin those trees and shrubs out so that there is less harborage area for the mosquitoes to rest during the day.
What You Can Do to Help Fight Mosquitoes:
1) Eliminate Potential Water Breeding Sources--
- Empty any standing water in old tires, buckets, plastic covers, toys, or any other container where eggs could be laid and larvae and pupae may thrive.
- Empty and change the water in bird baths, fountains, wading pools, rain barrels, and potted plant trays at least once a week, if not more often.
- Drain or fill temporary pools with dirt.
- Keep swimming pools treated and circulating, and keep rain gutters unclogged.
2) Protect Yourself Personally--
- Use mosquito repellents (containing DEET) when necessary and follow all label directions and precautions closely.
- Use head nets, long sleeves and long pants if you venture into areas with high mosquito populations, such as salt marshes.
- If there is a mosquito-borne disease warning in effect, stay inside during the evening and early morning hours when mosquitoes are most active.
- Make sure your window and door screens are "bug tight."
- Replace all outdoor lights with yellow "bug" lights, especially near the entrances to your house.
- Contact your local Mosquito Abatement District or County Environmental Health Department. Their phone number is frequently listed on your property tax bill. If there are large mosquito populations evident in your neighborhood, they will come out and try to eliminate the source if they can find it. If you have any questions about mosquitoes and their control they may also be able to help. You can also call Corky's Pest Control-we'd be happy to answer your questions.
Call Corky's for quality pest control services at reasonable prices! 1-800-901-1102
You can also call Corky's Pest Control-we'd be happy to answer your questions.
