AL.COM: Mosquitoes of Alabama: What makes them tick, makes you itch, and what you can do about it

Dennis Pillion | dpillion@al.comBy Dennis Pillion | dpillion@al.com
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on July 15, 2015 at 7:00 AM, updated July 15, 2015 at 7:32 AM

Each and every time you go outdoors in Alabama during the summer, you’re likely to be confronted by a ravenous animal, thirsty for your blood, that kills about 700,000 people every year worldwide.

That animal, if it’s female, would like nothing better than to suck up so much of your blood that her abdomen distends and swells more than twice its normal size, giving her enough nutrients to create around 200 eggs. After a day or two of digestion, she can deposit those eggs in any handy source of standing water, and in a little more than a week, both she and her children will be on the hunt, searching out another meal to keep the cycle going.

The animal is of course the mosquito, which can range from annoying pest to deadly disease carrier depending on your location. Alabama, with its richness of ecosystems and geography, is home to about 60 species of mosquito, according to Auburn University entomologist Derrick Mathias, but that’s just a drop in the worldwide bucket.

Mathias said the best estimate is that we share the planet with around 3500 distinct species of mosquito, and he’s spent much of his career studying them. Mathias studied mosquitoes in the Pacific Northwest and in Kenya before taking a job at Auburn last year. He even got a Masters degree in public health in addition to his PhD in entomology to better understand the disease-spreading capability of mosquitoes and ticks.

Though there are many species of mosquito, not all of them are after your blood, he said. Male mosquitoes do not feed on blood. That’s only necessary for females who are preparing to lay eggs.

Some species of mosquito need only plant nectar to complete their life cycles. Some are actually considered beneficial because they feast on other mosquito larvae early in their life cycle and then live on plant nectar as adults.

Mathias said many species rarely come into contact with humans because they live deep in woods or wetlands where people don’t often go. Some species that do require a “blood meal” prefer birds over mammals, though most are fairly opportunistic.

Some are vectors for diseases like malaria, dengue fever, yellow fever, and West Nile virus. Some carry the diseases but haven’t been shown to transmit them to humans. Some are non-carriers.

An invasive pest

One of Alabama’s most annoying and blood-thirsty species wasn’t even found in this hemisphere 40 years ago. Mathias said the Asian tiger mosquito (Aedes albopictus), is an invasive, imported species that didn’t reach the southeast United States until the mid-1980s.

Recent research has traced the arrival of the Asian tiger mosquito to shipments of used tires that arrived in Houston from Japan and other Asian countries about 30 years ago. The mosquito larvae survived the journey in tiny pools of standing water among the tires.

“What makes (the Asian tiger) different is that they don’t need much water at all,” Mathias said. “They’re really well-adapted to small containers.”

The Asian tiger mosquito has out-competed and largely replaced the so-called “yellow fever mosquito” (Aedes aegypti), in Alabama, Mathias said. While it’s tempting to celebrate the absence of yellow fever mosquitoes in the state, the Asian variety can carry most of the same diseases as its African cousin (which was also an imported species in Alabama), and tends to live in close contact with humans.

Unlike some species of mosquitoes, which prefer deep woods, the Asian tiger mosquito feels right at home in suburban areas and prefers feeding on mammals, especially those who live in two-story ranch houses with clogged gutters, stagnant bird baths or flower pots that collect water laying around. It has distinctive (as mosquitoes go) black and white strips on its legs and body, with a white stripe down its back.

Controlling the beast

Despite a number of interesting high-tech research studies into flying pest control, the best recommended tactics for mosquito control are the simple ones we’ve heard for years.

  • Eliminate pools of standing water around your home that they use to lay their eggs.
  • Avoid outdoor exposure in the hours around dawn and dusk.
  • Wear repellents with DEET, long sleeves and pants, and bright-colored clothing if you do go out in mosquito country.
  • Patch window screens or other gaps that may allow mosquitoes into your home.

Mathias said that mosquito eggs can hatch in about a week, depending on the species, so he would turn empty any bird baths or pools of standing water twice a week. For ponds or containers you can’t empty, several larvicides are available, usually in pellet form, that can kill larvae or pupae before they reach adulthood.

What’s in your insecticide?

Several local governments throughout Alabama spray for mosquitoes during the peak season, summer. According to the Environmental Protection Agency, the most common adulticide is called permethrin, which is sprayed from a truck or dropped from a plane. EPA says that 9 to 10 million acres of land annually are treated with permethrin each year. Permethrin is the most common of a class of similar insecticides called pyrethroids.

Pyrethroids are meant to be applied via ultra-low volume (ULV) aerosol sprays, to target and kill adult mosquitoes in the air, so it’s most effective during peak mosquito hours around dusk.

According to EPA, pyrethroids are not believed to pose “unreasonable” risks to human health or the environment, but are toxic to marine life and bees. One woman has filed a federal lawsuit against the city of Birmingham, claiming its mosquito spraying program was killing beneficial pollinators like bees and butterflies.

Mathias said that “off-target” impacts should be considered in mosquito spraying programs, or for people who use private services or purchase their own insecticides.

“It’s really a balancing act,” Mathias said. “Is it worth spraying or not? If you want butterflies in your garden, maybe it’s not.”

Mathias said some mosquitoes in Alabama have developed resistance to insecticides. Insecticide resistant mosquitoes are a particular concern in tropical areas where malaria kills hundreds of thousands of people every year.

Natural solutions

For those who don’t want to wage chemical warfare in their backyards, there are a number of natural predators or deterrents to mosquitoes that may help keep the populations in check, though possibly not enough to host a 7 p.m. dinner party on your back deck without expecting a few extra guests.

One of the most frequently mentioned mosquito predators, the bat, has been shown in laboratory tests to eat huge numbers of mosquitoes in relatively short periods of time. It’s much less certain, however, that bats can eat enough mosquitoes fast enough to be a one-stop solution to a pest problem.

There are several commercially available bat houses homeowners can purchase to provide habitat for voracious insectivores. Several species of birds eat mosquitoes as well, so having them around couldn’t hurt either, and if you have a pond, certain species of fish feed readily on mosquito larvae.

There are also a number of aromatic plants which are thought to repel mosquitoes or mask the smell of nearby people, including citronella, basil, lemon balm, mint, rosemary, marigolds, and geraniums.

High-tech options

While the simplest mosquito control methods can be the most effective, there are some new emerging techniques, including genetically modified mosquitoes. Florida-based company Oxitec is developing genetically-modified mosquitoes to infiltrate natural populations with less desirable traits.

According to the Oxitec web site, the company engineered a “friendly” male Aedes aegypti mosquito that they release into the wild. The friendly mosquito mates with females of its species but produces offspring that do not survive to adulthood.

Florida officials are reportedly debating whether to try the GMO approach in the Florida Keys, where A. aegypti have begun developing resistance to pesticides and where diseases like dengue fever and chikungunya are more of a threat.

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