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Mosquito Coast 

On the trail of Culex pipiens

Wednesday, Jul 2 1997
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A green Alameda County pickup truck stops outside Urban Ore, the gentrified junkyard in the Berkeley flats, on a recent weekday afternoon. The driver, a 30-ish woman in white work coveralls and brown work boots, hops out.

She makes her way past a stack of windows, half an old wooden staircase, and an indoor jacuzzi tub, arriving at a row of toilets in just about every imaginable shade of pastel. She peers intently into each bowl, pausing once to flip open the lid of a rose-colored one. She smiles with satisfaction: Nothing but a few inches of water from the recent rains, and the liquid is relatively clear.

As she enters the shack that serves as Urban Ore's office, the manager, a stocky, round-faced man, grins and welcomes her with familiarity: "Hey, there's Mosquito Lady."

"Mosquito Lady," Alameda County Mosquito Control Technician Lee Holt, grins back -- and asks him to please have someone dump the water that's accumulated in the open toilet bowls. The toilets are currently mosquito-free, but the pools of rainwater are prime sites for mosquito larvae to hatch.

The junkyard toilet inspection complete, Holt jumps back in the truck and moves on. It's just one small part of her role as an employee of the Alameda County Mosquito Abatement District -- one of the MADmen and MADwomen, as some district workers jokingly refer to themselves. (A little mosquito humor there.)

Holt is equipped with an unusual arsenal for her killing mission: a milk can of live fish, a tub of ground-up corncobs, and some charcoal briquettes. Her targets: the millions of mosquitoes that spawn and thrive in the wettest, smelliest corners of Alameda County.

During the day, the mosquitoes of Alameda County are virtually invisible. But at night, the feasting begins.

Most of the county's biting mosquitoes are "night biters," which carry out nocturnal raids on human prey. (Only the females are bloodsuckers. The males feed on plant juices.)

When mosquito-weary residents pushed the county to create a special mosquito control agency in 1930, marsh mosquitoes were the main problem. Since then, however, the so-called "cosmopolitan" mosquitoes that thrive near human habitations became the primary pests.

Holt and six other technicians with the Mosquito Abatement District now battle 19 species of mosquito. The district, funded by property taxes and a special tax, is one of 50 mosquito control agencies in the state.

Services -- free to county residents -- include telephone and on-site consultations and supplying guppy-size mosquito-eating fish for fish ponds. And yes, they deliver.

Eight of the 19 species of mosquito that live in Alameda County have been classified as "serious pests," according to the agency. These species have been specifically noted as the most troublesome to people and their pets.

The two worst offenders are the house mosquito (Culex pipiens) and the fish pond mosquito (Culiseta incidens). These two species account for 70 percent of all the agency's service calls. Aggressive, day-biting marsh mosquitoes, belonging to the Aedes family, are a presence. But these are less of a nuisance in urban areas, because they tend to stick to the marshes around the bay.

In addition to these pest mosquitoes, whose bites only cause minor irritations, Alameda County also has several species that can carry diseases. These include dog heart worm and -- most worrisome -- malaria and encephalitis. Alameda County has never recorded a case of either of the human diseases being contracted from an indigenous insect. Still, the agency monitors the county for those mosquitoes year round.

The Mosquito Abatement District reports increasing numbers of residents are requesting its services, though no one knows if that means merely that more Alameda County residents are becoming aware of the abatement district, or if the mosquito population is actually growing. Last year, the district made 2,100 service calls and delivered more than 50,000 fish, compared to roughly 46,000 in 1995.

March through June is generally the busiest time of year, though salt marsh mosquitoes breed whenever it rains.

A typical day for Technician Holt means as many as 10 service calls to homes, businesses, and open spaces in a wide-ranging area that includes Berkeley, Emeryville, and Alameda, extending from Tilden Park south, and east through the Berkeley and Oakland hills. Residents' penchant for fish ponds -- Holt says there are over 1,000 artificial and natural ones -- makes the area especially mosquito-prone.

"Really gross, icky, skanky water -- they love it. I can just smell them," Holt says vehemently. "The mosquitoes go, 'Hey there's a nice home for us.' "

Some of the best sources for the nastiest water are catch basins and storm drains. They are choice breeding areas for mosquitoes -- as are untended birdbaths, pails of dirty water, and gutters. Even something as seemingly innocuous as an old tuna can that's caught some raindrops can nurture enough bugs to drive an entire block nuts, she says.

This afternoon, she stops to check the fish pond behind a house on Colusa near Marin in Albany, a notorious breeding source that Holt has been treating for the past few months. The pond, usually thick with mosquito larvae, is clean. The mosquito fish are thriving. But the woman who owns the house says she is still getting bitten.

Holt is stumped.
She searches the back yard for possible sources, checking drains and sumps that have been covered by foliage, but there's no sign of mosquitoes. Holt pauses a moment, hands on her hips, and then raises an index finger to determine the direction of the wind.

Holt gives this assessment. "I'm guessing your house is right here, the storm drains are down the street, and there's a bit of a breeze, so it's an easy meal for the mosquitoes."

Once the source of the problem is found, treatment is fairly simple. The district prefers nontoxic, biological methods: mosquito fish, briquettes, and corncobs for fish pond mosquitoes; larvicidal oil and briquettes for house mosquitoes. Stronger, inorganic chemicals are used only in emergencies.

A single 2-inch mosquito fish, for example, can eat more than 100 larvae a day. The corncob particles are treated with a bacteria that specifically targets mosquito eggs. The briquettes release another anti-mosquito bacteria that kills adolescent mosquitoes. Both dissolve after a few days.

Down the street from the Albany fish pond, a few minutes away, Holt removes the grate from a drain at the intersection of Marin and Colusa. The water below seems to twitch. It is alive with mosquito larvae, each less than a quarter-inch long, "wrigglers," as they are known in mosquito parlance. It is just as Holt suspected.

After a few shots from her spray bottle of larvicidal oil, hundreds of the tiny, writhing, curling creatures surface, vainly struggling for survival.

Holt seems satisfied -- vindicated, almost.
She agrees that being a mosquito technician is hardly a high-recognition job, but overcoming the challenges it poses can be rewarding.

"I have to be a detective every day and solve a different crime," she says. "You have to think, 'If I were a mosquito and I wanted to find an obscure spot, where would I go?' It just gets to a point where they get so darned sneaky.

About The Author

Tara Shioya

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