One of the benefits of the dry conditions so far this summer was a lack of salt marsh mosquitoes, but brace yourself. They could be swarming soon.
Experts say that Thursday's and Friday's storms, which brought more than an inch of rain to many areas of the Lowcountry, may trigger an outbreak this week -- just in time for the American Mosquito Control Association's National Mosquito Control Awareness Week this week, through July 2. The goal of the week is to educate the public about mosquitoes and the services provided by mosquito control workers.
Charleston County mosquito control field inspector Chad Cashwell, said the lack of rainfall "just sets us up for a huge outbreak when we do finally get some rain."
In dry conditions like we've had, mosquito eggs lie dormant, waiting for a good rain to hatch. High tides usually bring surges in population too. Mosquitoes need water to emerge, and larva live their first few days in the water.
Outbreaks typically follow about four days later.
"We are probably setting up for a very busy late fall," said Charleston County mosquito control superintendent Donna J. Odom. "Last year started off slow too, and then we treated and sprayed until just before Thanksgiving."
She said the area needs a couple more downpours like Thursday's to trigger a big outbreak.
Benjamin Milligan, supervisor with Berkeley County Mosquito Abatement, agreed.
"It's been OK so far this year," he said. "Now last year, with all the rain we had at the end of the season, we were really busy. That might happen again this year. You just never know."
County mosquito taxonomist Ed Harne said the salt marsh can produce 8 million females per acre every time it rains. Dredge disposal sites, such as the one in the Charleston Harbor, can produce 10 times more, leading to lots of mosquitoes on the Charleston peninsula or in Mount Pleasant.
Females, which feast on blood from humans and other animals to get the nutrients they need to develop eggs, typically live two to three weeks.
"They don't all hatch at once either," Harne said. "They have a sort of built-in survival feature and some will wait until the next rainfall."
However, while residents may have had a break from bites while the salt marsh mosquitoes lie in wait, many folks have unknowingly set up their own Asian tiger mosquito breeding grounds in flower pots, bird baths and kids' toys left in the yard.
"A lot of people have beautiful yards, but they are a harbor for mosquitoes," Cashwell said.
Mosquitoes can breed in any standing water.
"I've even seen them breed in bottle caps," Cashwell said.
When residents call Charleston County Mosquito Control for help, one of the first questions they are asked is what time of day the mosquitoes bite. Asian tigers come out during the day while salt marsh mosquitoes come out at dawn and dusk.
"Of course, we can't go to everybody's house," Odom said. "We have a rain, and then a few days later, we start getting calls, but the best way to deal with mosquitoes is to get rid of the source. A lot of people don't believe that mosquitoes can come from a cup of water or the top of a can that's been left outside."
Milligan agrees that education is the key for most people.
"We go out and teach homeowners about getting rid of containers and anything that can hold water," he said. "Because if they aren't going to do that, there ain't no use for us to spray."
Odom said the volume of calls has increased in the last few years as people have become more aware of mosquito-borne diseases, particularly West Nile virus.
Mosquitoes in South Carolina may carry West Nile or eastern equine encephalitis, making it important to control the mosquito population, monitor for diseases, and protect ourselves, according to the state Department of Health and Environmental Control.
Mosquitoes become infected when they feed on infected birds. Within two weeks, a mosquito can transmit the virus to another bird, animal or human through its bite.
Many types of mosquitoes may carry the virus, including the Southern house mosquito, which is common here.
Because Southern house mosquitoes breed anywhere foul water stands, the lack of rain does not help keep potential West Nile cases at bay, said Chris Evans, an entomologist with DHEC's Bureau of Laboratories.
"The lack of rain causes water to stagnate, and that's where the mosquitoes like to breed," he said.
He said no cases of West Nile had been found in South Carolina this year as of June 17. As of then, the lab had tested 11,400 mosquitoes from 422 pools - mosquitoes collected from the same location on the same date - in 14 counties, including Charleston and Berkeley.
"We usually see our first case around the end of June," he said. That could be in a human, animal, bird or mosquito. Peak season for West Nile is July through September. During that time, he examines mosquito samples collected twice a month.
Last year, West Nile was found in 11 mosquito pools in Sumter County.
Never going away
Mosquitoes' ability to adapt to changing environments makes them nearly impossible to eradicate, according to the American Mosquito Control Association. Additionally, experts say that if they were, they would be replaced by another pest that could be worse.
For that reason, local mosquito control employees know they have a certain level of job security.
"I don't think we could ever get rid of all the mosquitoes," Cashwell said.
Charleston County, with 16 employees, has one of the biggest mosquito control programs in the state. In this area, preparations for mosquito season start in February and spraying starts in April and runs through October or November.
Inspectors check rain gauges, examine standing water for larva, assess the number of mosquitoes that land on their bodies in a certain time period, put out source-reduction remedies and collect specimens from traps for lab testing.
"We have locations that we've been tracking for years," Cashwell said. "We can't know all the ponds and puddles in the county, but we know where standing water usually collects and we try to focus on those areas."
Information collected by inspectors is used to determine where trucks will spray each night during mosquito season. Charleston County also uses a helicopter when necessary. In the off-season, the county's mosquito control division spends time on public education and retooling for the next season.
Mosquitoes are known from as far back as the Triassic Period, 400 million years ago, and from North America from the Cretaceous, 100 million years ago.
The name mosquito actually means 'little fly.'
There are about 2,700 species of mosquito worldwide; 176 species in the United States; and 61 species in South Carolina.
Female mosquitoes ingest blood so that their eggs can mature prior to laying. It serves no nourishment function. Males do not take blood meals at all. In order to get energy, both male and female mosquitoes feed upon plant nectars — much in the same manner as honeybees.
The average mosquito weighs about 2.5 milligrams.
The average mosquito takes in about 5-millionths of a liter of blood during feeding.
Mosquitoes find hosts by sight (they observe movement); by detecting infrared radiation emitted by warm bodies; and by chemical signals (mosquitoes are attracted to carbon dioxide and lactic acid, among other chemicals) at distances of 82 to 115 feet.
Mosquitoes fly an estimated 1 to 1.5 mph.
Salt marsh mosquitoes can migrate up to 40 miles for a meal. The Asian Tiger mosquito has limited flight range of about 300 feet.
Carbon dioxide is the most universally recognized mosquito attractant and draws mosquitoes from up to 35 meters. Bigger people are often more attractive to mosquitoes because they are larger targets and they produce more mosquito attractants.
Active or fidgety people also produce more CO2 and lactic acid.
Women are usually more attractive to mosquitoes than men because of the difference in hormones produced by the sexes.
Blondes tend to be more attractive to mosquitoes than brunettes.
Smelly feet are attractive to mosquitoes — as is Limburger Cheese.
Dark clothing attracts mosquitoes.
Movement increased mosquito biting up to 50 percent in some research tests.
A full moon increased mosquito activity 500 percent in one study.
- American Mosquito Control Association (mosquito.org) and the South Carolina Department of Health and Environmental Control
ALL ABOUT REPELLENTS
Repellents do not kill mosquitoes and other insects, but they will help deter them from biting people.
DEET remains the standard by which all other repellents are judged. DEET, developed by the U.S. Department of Agriculture, was registered for use by the general public in 1957. It is effective against mosquitoes, biting flies, chiggers, fleas, and ticks. The American Academy of Pediatrics says products containing up to and including 30 percent DEET can be used on children 2 months of age and older.
Recently, new products have been registered with the EPA that come close to the effectiveness of DEET:
Picaridin (also known as KBR 3023 or Bayrepel). Can be used on children 2 months and older.
Oil of Lemon Eucalyptus (also known as PMD). This is a synthesized version of oil of lemon eucalyptus, not the pure (essential) oil of lemon eucalyptus, which is not registered with the EPA as an insect repellent. Products containing oil of lemon eucalyptus should not be used on children under 3.
IR3535 has been used as an insect repellent in Europe for 20 years with no substantial adverse effects. No specific age restrictions have been developed for the use of IR3535 on children.
Rules to follow
Here are some common sense rules to follow when using repellents:
Apply repellent sparingly only to exposed skin.
Do not inhale or ingest repellents or get them into the eyes.
Avoid applying high-concentration products (more than 50 percent DEET) to the skin.
Avoid applying repellents to portions of children's hands that are likely to have contact with eyes or mouth.
Pregnant and nursing women should minimize use of repellents.
Never use repellents on wounds or irritated skin.
Use repellent sparingly, but be sure to cover all exposed skin. A mosquito can find an unprotected spot the size of a dime.
Wash repellent-treated skin after coming indoors.
Source: American Mosquito Control Association (mosquito.org)