Michelle Byrne Walsh is the editor of the State-by-State Gardening magazines Missouri Gardener, Indiana Gardening, Ohio Gardener and Pennsylvania Gardener. She is also a master gardener and member of the Garden Writers Association.

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Buzz Off, Mosquito
by Michelle Byrne Walsh    

It’s hard to wax poetic over the lowly mosquito—especially with West Nile virus. But mosquitoes deserve to be understood. (Then you can swat them.)

It was a perfect Sunday morning. I had a huge cup of coffee in one hand and the fat Sunday paper in the other. I went outside to sit on the deck and watch the sunrise.

Then, with both hands occupied, a mosquito landed on my arm. I put down the paper, swatted the beast, and picked up the paper again. But before I could even get the comics out, another mosquito landed on my leg. This time I put down the coffee cup and smashed him, too. Then a Kamikaze mosquito began buzzing my ear. I flailed at him and spilled my coffee all over.

A minute later, I was sitting at the kitchen table.

Mosquitoes have always been bothersome to gardeners because we are outdoor people. When not working in the garden we tend to be taking walks, manning the barbeque or enjoying a leisurely cup of morning coffee — these activities usually take place during peak mosquito-biting times: dawn and dusk. Granted any mosquito bite is itchy and bothersome. But here in the Midwest, thoughts of mosquito-borne diseases—including deadly diseases such as malaria, yellow fever and dengue fever — seldom crossed our minds.

That is until 2002, when West Nile virus first appeared in the Midwest. These days a mosquito bite doesn’t seem quite so inconsequential. However, with diligent mosquito bite prevention, mosquito control techniques, and a bit of knowledge about West Nile virus, gardeners can stop worrying (if just a little).

The Secret Life of a Mosquito

According to the American Mosquito Control Association in North Brunswick, New Jersey, there are more than 3,000 species of mosquitoes throughout the world; about 176 species occur in the United States. The AMCA notes mosquitoes are insects belonging to the order Diptera, the “true flies.” Like all true flies, they have two wings, but mosquitoes’ wings have scales. Female mosquitoes’ mouthparts form a long piercing-sucking proboscis. Males differ from females in that they have feathery antennae and their mouthparts are not suitable for piercing skin. Males also do not feed on blood; they eat only nectar.

When a female bites you, she injects salivary fluid into your skin, which produces the swelling, irritation and familiar itch. Many mosquitoes also inject microorganisms, which can transmit diseases — including malaria, encephalitis and canine heartworm. 

Mosquitoes have four distinct life stages: egg, larva, pupa and adult. The entire lifecycle — from the laying of eggs to a mature adult mosquito — is completed in about 10 to 14 days.

Egg—female mosquitoes lay their eggs in water or on moist substrates. Many mosquitoes, including Culex spp., lay their eggs in floating clumps called “rafts.”  

Larva—Eggs hatch into larvae, or “wrigglers,” which live in the water and feed on organic matter. They go through a number of “instars” or growth stages. Mosquito larvae are eaten by fish and other insects. 

Pupa—A larva develops into pupa. After two days, an adult mosquito emerges from the pupa. The new adult rests on the water’s surface until its body dries and its exoskeleton hardens. 

Adult—Female mosquitoes require a blood meal before they can lay eggs, so only female mosquitoes bite. They bite animals (warm or cold blooded) and birds every few days during their adult lives, which may last several weeks. Both male and female mosquitoes feed on nectar. 



A female mosquito Credit: Joseph Berger, Bugwood.org

Sidebar sources: USDA National Pest Alert, American Mosquito Control Association, University of Illinois Extension

History of West Nile Virus

Look back in recent history and you’ll realize West Nile virus is not the first encephalitis-type disease to affect Midwest residents. In 1975, St. Louis encephalitis spread through the area. Since the 1970s, scattered cases or outbreaks of St. Louis encephalitis have been reported. And the reason this is important is this: St. Louis encephalitis and West Nile virus are “sister” diseases — similar in several ways. Therefore, we can and will learn to live with West Nile virus, just as we learned to live with St. Louis encephalitis. Both West Nile virus and St. Louis encephalitis are “arboviruses” (arthropod-borne viruses, which are transmitted between susceptible vertebrate hosts by blood-feeding arthropods like mosquitoes and ticks). There are several kinds of arboviruses, including La Crosse encephalitis, western equine encephalitis and eastern equine encephalitis.     

West Nile virus, like St. Louis encephalitis, is carried by birds (the hosts), then spread to humans, horses and other animals. Mosquitoes bite the birds with the virus, and then the mosquitoes transmit the virus by biting other animals, including us. West Nile virus is transmitted by several species of mosquitoes, most often the Culex pipiens mosquito (aka the northern house mosquito).

Other mosquitoes carry maladies that are usually not a problem in the Midwest. The Aedes genus is responsible for the spread of yellow fever and dengue; the Anopheles genus transmits malaria.

In 1999, the mosquito-borne West Nile virus first appeared in the United States. Previously it had been in Europe, the Middle East and Africa, including Israel and Egypt. But in 1999, 62 human cases and seven deaths were reported on the East Coast of the U.S., according to the Centers of Disease Control. By 2002, the disease had spread through the East, Midwest, Southeast, Plains states and Texas and California.

What Are the Symptoms?

In 2012, there were 5,674 cases of West Nile virus reported to the Centers of Disease Control nationwide and 286 deaths from West Nile virus.

According to the CDC, most people (about 70 to 80 percent) who become infected with West Nile virus do not develop any symptoms. If a person does develop symptoms, they are similar to the flu, including a moderate to high fever, headache, sore throat, stiff neck, rash, swollen lymph nodes and muscle weakness. The CDC states, “Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.” Severe symptoms might show up in a few people. The CDC notes, “Less than 1 percent of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis. Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent. About 10 percent of people who develop neurologic infection due to West Nile virus will die.”


A northern house mosquito (Culex pipiens) Credit: Susan Ellis, Bugwood.org

Which Mosquito?

Although several types of mosquitoes can carry West Nile virus, the northern house mosquito (Culex pipiens) is the most likely vector. Culex mosquitoes are often out around dawn and dusk throughout the warm season, but are most numerous from mid-June into fall.

Culex mosquitoes like to lay their eggs in stagnant, stinky water like in clogged gutters. Abandoned pools, junk yards, and discarded tires — anything with greenish water — are a breeding ground for the Culex mosquito.

Smart Mosquito Control

So what is a gardener to do?

Mosquito control truly starts at home — ridding the yard of stagnant water and taking precautions when venturing outdoors during peak biting times. In addition, many cities and towns spray adulticides (which kill flying adult mosquitoes) to knock down mosquito populations.

Protect yourself from mosquito bites:

  • Apply DEET-containing insect repellent sparingly to exposed skin. The more DEET (N,N-diethyl-meta-toluamide) a repellent contains the longer time it can protect you from mosquito bites. A higher percentage of DEET in a repellent does not mean that your protection is better — just that it will last longer. Follow the manufacturer's directions. When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid children's eyes, mouths and hands. (Children may put their hands in their mouths.)
  • When possible, wear long-sleeved shirts and long pants outdoors.— Place mosquito netting over infants in carriers.
  • Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times.
  • Install or repair window and door screens so mosquitoes cannot get indoors.

Reduce the number of areas in which mosquitoes can breed:

  • Drain sources of standing water in your yard. At least once or twice a week, empty standing water from flower pots, pet water dishes, birdbaths, swimming pool covers, buckets, barrels and cans. Do not allow swimming pool water to become stagnant or untreated. Check for clogged rain gutters and clean them out.
  • Add mosquito-eating fish (such as goldfish, fathead minnows, mosquitofish and golden shiners) or a fountain or waterfall, to your water feature.
  • Use Bacillus thuringiensis israelensis (Bti) “donuts” in ponds without fish or other areas of standing water. 

Save your money — ineffective mosquito products:

  • Bug zappers
  • Light traps
  • Mosquito-repelling plants (they repel mosquitoes only within inches of the plant)
  • Citronella candles and lamp oils (not enough area coverage)
  • Electronic emitters

 

Posted: 07/15/13   RSS | Print

 

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