When Mosquitoes Attack!

There was a gentleman in the Home Depot parking lot one recent Saturday wearing a mosquito-net jacket.

“It really works,” he said with a nod, a wink and two thumbs up. His wife added, “You can get it at Safari Unlimited!”

Safari Unlimited better stock up. According to Dr. Henry Lewandowski, director of Chatham County Mosquito Control (CCMC), Savannah is home to “the largest man-made mosquito breeding grounds in North America.”

The breeding grounds he’s talking about are the Savannah River dredge spoils located across the river from downtown. The next time you’re going over the Talmadge Bridge, look off to your right, past the Westin Harbor Golf Course. You can’t miss the 7,000-acre sandbox known as the spoil containment area.

Sediment brought up from the bottom of the river rises 52-feet into the air in places, reshaping the lowlands’ topography and providing an ideal hatching site for the salt marsh mosquito, a notoriously aggressive species known for assaulting its victims at all hours of the day.

Luckily, Dr. Lewandowski says that salt marsh mosquitoes are not common carriers of the West Nile virus. But while they are not the “primary vector” for West Nile, they do make the CDC list for species testing positive for the virus.

Dr. Lewandowski estimates that some 100 million mosquitoes emanate from the dredge spoils in a season and from “there inundate the entire county.”

While salt marsh mosquitoes migrate long and far, the mosquito most likely to transmit West Nile virus likes to stay close to home. The Culex pipiens species breeds in hot, damp, urban areas -- places like downtown Savannah.

Dr. Lewandowski says that his department calls downtown the “Hot Zone.” The exact borders, he says, are the Savannah River to DeRenne Avenue, stretching from Wilmington River to I-516.

The Hot Zone is home to nine out of ten cases of West Nile virus in the County. Since birds are so susceptible to the virus, the county keeps “sentinel chickens” as a sort of advanced warning system. These chickens routinely test positive for the virus.

Four years after West Nile was discovered for the first time in the U.S., the first human cases showed up in Savannah. Chatham County rolled out an adulticide campaign, meaning they targeted adult mosquitoes by spraying massive amounts of pesticides over the Hot Zone.

Hot zone? Sentinel chickens? If this is starting to sound like a full-scale military campaign, it’s not far from the truth. 100 million mosquitoes breeding and striking downtown Savannah from across the border, meeting a small but determined resistance armed with trucks, airplanes, helicopters and chemicals.

 

War is being waged as Savannahians eat, sleep, work and play. For the most part, we are oblivious to the dangers of living in a war zone, both from the enemy and from the collateral damage inflicted by the weapons used to fight the enemy.

When the Hot Zone “went hot” in 2003 with the first reported cases of West Nile in the County, Mosquito Control was spraying a low volume concentration of Malathion, an organophosphate insecticide that jams up the nervous system in insects and in humans.

But somehow the Malathion didn’t seem to be working on Savannah’s mosquitoes.

The CDC tested mosquito eggs sent from Savannah and confirmed what the county had suspected. No matter how much they shrouded the city with insecticide, they weren’t getting results. The mosquitoes had developed a resistance to the chemical. Resistance is commonly known to be the result of chemical overuse.

The timing was inopportune; the Hot Zone was in the middle of a West Nile outbreak. By the end of 2003, there were eight confirmed cases of the Virus in the Hot Zone, and one just outside of the Hot Zone’s borders. One person died.

The Malathion wasn’t entirely ineffective. It worked well on many other kinds of insects, including a small species of wasp that preys on an even smaller insect called “kermes scale.” Without the wasps, the kermes scale population exploded and their food source, Savannah’s live oak trees, took the hit.

In the spring of 2004, oaks throughout downtown started to turn brown, their limbs withered. The mosquito wars had inadvertently created an entirely different kind of infestation.

Bill Haws, the administrator for Savannah’s Park and Tree department, remembers hearing a lecture at a seminar about a similar problem in South Carolina, which was determined to be caused by mosquito control insecticides killing off the beneficial wasps.

Haws, though careful not to point fingers at Chatham County Mosquito Control, admits that the “pesticides they use are harmful to beneficial insects.” When that happens the “balance of nature gets out of whack,” he says.

In an effort to pop nature back into balance, the City performed its first beneficial insect release, letting go 60,000 predatory wasps in squares and parks all over the Hot Zone.

It seems to have worked, Haws says. In 2005 the oaks returned to a healthy green.

By then Mosquito Control had switched over to a compound called Naled, which is corrosive enough at high volume to take the paint off cars; it is also classified as a reproductive toxin for humans.

When discussing chemicals used in mosquito control, Dr. Lewandowski focuses on the “ultra-low volume” of the pesticide -- one ounce per acre.

“We’ve undergone a real paradigm shift here,” he says. Environmental concerns, cost increases for chemicals, and improving spraying techniques and technology have all combined for a more selective, targeted approach to the application of pesticides.

He continually steers the conversation back to his “biggest problem.” The dredge spoils.

“They never really dry out,” says Dr. Lewandowski, flipping his hands over palms side up on his desk. The top of the dredge spoils dry in the hot sun, then crack, creating thousands of little hatcheries.

The thing about mosquito eggs is that they can lay dormant for months, and then with a bit of water in a deep crevice, you have mosquito magic.

The County keeps two amphibious tractors out at the spoil site, trying to drain water from river bottom sediment by creating ditches and slinging mud around. They douse the area with larvacide mixed with sand in an effort to penetrate the fissures where the mosquitoes breed.

But this technique is imprecise, and resistance to the Methoprene used as a larvacide is always a concern.

 

While the threat of West Nile is a relatively new danger, the Savannah mosquito wars have been raging for quite some time. Chatham County established its mosquito control division in 1957 to counteract the nuisance of salt marsh mosquitoes. In 1960, the Army Corps of Engineers built the spoil containment site, setting the stage for a real battle.

A headline in the New York Times from the summer of 1984 reads “Savannah, Ga., Braces for Mosquito Invasion.” The article states, “Billions of mosquitoes headed downwind toward Savannah today, as they do each year from their South Carolina breeding grounds.”

Migratory by nature, the salt marsh mosquitoes fan out across the region, snacking on our legs and laying eggs in high marsh. The eggs can lie dormant for years, ready to hatch when a full moon pulls the tide high, creating flood pools where the eggs then hatch off and become larvae.

The primary mosquito vector for West Nile is also perpetuated by floodwaters. After a typical summer deluge, its eggs will wash down into the city’s catch basins with grass clipping and other debris.

“They absolutely prefer polluted waters,” says Dr. Lewandowski. And once they hatch, they stay pretty close to their breeding ground, primarily urban storm drains, retention ponds, and even sewage treatment lagoons.

The days after heavy rains are busy times for the County’s mosquito control team. Larvacide is dropped into the Hot Zone’s storm drains and over the dredge spoils.

The County’s six entomology experts are busy surveying area waters for signs of larvae populations to treat with Methoprene, a growth regulator, which Dr. Lewandowski credits as being “extremely effective.” But he admits there is “no way we can prevent all adult mosquitoes from hatching off.”

That’s when you’ll hear the rotors of low-altitude choppers and the drone of the fogging trucks. Chatham County spends $837,000 on mosquito control chemicals annually. They respond frequently to calls from the riverfront community “screaming for help,” says Dr. Lewandowski.

Much like the Air Force might, Mosquito Control works off of known “target lists” of high-profile breeding areas.

Mosquito Control Chief Entomologist Susan Bruce says newly cleared areas in the county slated for development can be particularly problematic, with the human activity in effect increasing the opportunity for mosquitoes to breed in stagnant water.

“Sometimes they clear the trees and leave big ruts in the ground from the heavy equipment, and that can cause a major, major problem for us. And a lot of that new development is right next to hardwood swamps,” she says.

Hutchinson Island Golf Club and Fort Jackson are close to the dredge spoils, and were the first to call Mosquito Control this year after tropical storm Alberto dumped enough rain to kick off a breeding bonanza.

While Mosquito Control most often sprays the poisons in the evenings around sunset when many of the 38 species of mosquitoes in the County like to dine, they’re also experimenting with different times of day to enhance the dispersal and drift pattern of the pesticides.

Dr. Lewandowski attributes the timing of the pesticide application as a primary reason that there were no reported cases of West Nile Virus in the County last year. Though he also adds that the virus is cyclical in nature and could be on a down cycle. A likely scenario, given that West Nile cases were down across the Eastern Seaboard in 2005.

Outside of the Hot Zone, in Savannah’s suburban neighborhoods and on the islands, Mosquito Control uses truck-mounted foggers to spray a synthetic pyrethroid.

Dr. Lewandowski explains that because the trucks have a closer proximity to people, he prefers not to use Naled like he does aerially in the Hot Zone.

“Naled does tend to sting the eyes briefly,” he says.

The synthetic pyrethroid used is Resmethrin, which is registered with the EPA as a reproductive and developmental toxin. The label for the brand name it is sold under, Scourge, states that it is “highly toxic to fish.”

Dr. Richard Lee of the Skidaway Institute for Oceanography says, “Anytime we mess around with the balance of nature we usually pay a price.”

Dr. Lee says his “concern would be toxicity to shrimp and crabs. Any compound that kills insects, almost always kills shrimp and crabs.”

Then there are the honeybees. Ted Dennard of Savannah Bee Company says, “Anytime they spray, it is a massive loss. By morning there is a pile of dead bees on the ground and dead ones stuck in the hive.”

“Isn’t there something else they can use?” wonders Dennard.

 

CCMC is already using mosquito fish as a biological control, but the fish are only effective in permanent bodies of water like lakes, some culverts and even ditches. Beginning this year, the county will try a microbacterial larvacide known as Bti. It’s the same stuff in the over-the-counter “Mosquito Dunks” that you can buy at Home Depot.

Bti is the least toxic larvacidal control and has been used effectively for years in mosquito control programs all over the country. Basically it is a bacterium that is toxic only to the mosquito larvae that eat it.

Dr. Lewandowski says the County will try the bacterial larvacide this year for the first time in the Hot Zone’s catch basins, but he is unwilling to commit to its long-term use and says that it is too expensive to use on the dredge spoils.

This year CCMC received much needed reinforcements in their battle against mosquitoes from the state Department of Transportation. They’re kicking in $400,000 for mosquito control in the spoil area, which is over the state border in South Carolina and is privately owned by the Georgia DOT. Dr. Lewandowski says the county spends at least $600,000 on mosquito control at the spoils alone.

When the Savannah River Deepening Project moves forward, new mountains of sediment will appear, making expansive new hatching grounds for the mosquitoes. When that happens, Dr. Lewandowski and his band of fighters will be there with every tractor, truck, airplane, chopper and sprayer they can get their hands on.

And you just might better invest in that mosquito-net jacket. They’re acceptable attire at most local events, at least through Labor Day.  ƒç

 

Stacey Kronquest is a local freelance journalist. To comment, e-mail us at [email protected]

 

 

Mosquito Control by the numbers

Total staff: 30

Staff entomologists: 6

Years in current facility: 3

Number of trucks: 5

Number of truck routes: 54

Airplanes: 2

Helicopters: 2

Pilots: 1 -- Scott Yackel is Mosquito Control’s licensed pilot for fixed-wing and rotary wing aircraft. He also serves as helicopter pilot when Savannah Metro Police use one of Mosquito Control’s helicopters.

Helicopters shared with Savannah Metro Police: 1 -- Well, actually both of Mosquito Control’s helicopters are on call for police use. The special tracking devices and “Night Sun” spotlight that police use are fitted to either chopper depending on which is ready to fly a mission.

Though a helicopter is always available for police use, both choppers are owned and maintained by Chatham County Mosquito Control on behalf of the taxpayers.

Annual pesticide cost: $837,000 and rising

 

 

Kick it over!

There are 38 species of mosquitoes in Chatham County, many of which prefer to live close to people. All those containers we keep scattered about--birdbaths, planters, toys, gutters, trash bins, etc.--make wonderful hatcheries.

Take the Asian Tiger mosquito, for example. It has a taste for human blood and lays eggs in dark recesses where rainwater can collect.

To avoid becoming an unsuspecting breeder of the Tiger, kick over any container that might contain stagnant water. If you have any desire to sit outside this summer, get out your ladder and clear your gutters.

It’s a nasty job, but when August rolls around, you’ll be glad you did.

 

 

When the spray comes down

It can sometimes be unavoidable to prevent pesticide exposure given its wide scale application, but the Public Interest Research Group recommends you try to do the following:

• If you get sprayed, shower immediately. If you believe that you are experiencing symptoms as a result of pesticide exposure, call your doctor or poison control center.

• Keep windows shut and air conditioners off during and after spraying for as long as possible.

• Bring pet dishes, toys, laundry and other portable objects inside.

• Cover outdoor furniture, barbecue grills, sandboxes and play equipment and rinse off surfaces that cannot be covered before use.