A war on an enemy that's out for blood Buzz: No one wants mosquitoes, but environmental regulations are less tolerant of traditional pesticides. Natural pest controls may upset the ecological balance -- or cost too much.

June 10, 1997|By Frank D. Roylance | Frank D. Roylance,CONTRIBUTING WRITER

The mud sucks at Dennis Earling's feet, and gnats orbit his head as he enters a swampy neck of woods off Lodge Farm Road.

The state mosquito inspector edges close to a stagnant puddle, cocks his arm and strikes. In a flash, his long-handled plastic ladle scoops up his prey -- dozens of wriggling mosquito larvae smaller than grains of rice.

Earling sprays a larvae-suffocating film of mineral oil and moves on. The puddle near residential areas in eastern Baltimore County is just one stop in the 20,000 miles he patrols each season as a foot-soldier in the state's campaign against the mosquito.

The Maryland Department of Agriculture is assigned to subdue mosquito-borne disease and ensure that taxpayers can enjoy their back yards. But its Mosquito Control Section battles the worst of Maryland's 50 species in a swamp of conflicting public interests:

Attempts to replace some chemical and biological treatments with more "natural" pest controls have been blocked by the Department of Natural Resources as threats to the balance of life in the marshes.

With less freedom to try alternatives, the agency is left with increasingly costly sprays. In a political climate that demands less spending, more communities are being asked to endure more bugs.

Marylanders' tolerance for mosquitoes does not appear to improve when people migrate to outlying waterfront communities. Many people want to reside in a "natural" environment, but they want it purged of bugs.

Alma Rouse, her husband and two children moved two years ago from Dundalk to Millers Island -- a tiny community in eastern Baltimore County isolated by marsh.

"We love it down here," she said. Mallards forage in her front yard, and she has watched bald eagles from her back porch. "But I don't like the mosquitoes. I'd love to see something done about the mosquitoes, but I don't want anything to hurt the environment."

Recent rains may lead to a baby boom among the freshwater mosquitoes that prefer temporary puddles and pools. They are aggressive biters and carriers of dog and cat heartworm.

On the other hand, the mild winter and continued rains should help native fish keep salt-marsh mosquitoes in check.

Mosquitoes are not just an annoyance. Control efforts have kept Maryland free of home-grown malaria since the 1920s. Eastern equine encephalitis, carried primarily by salt-marsh mosquitoes, remains a threat to poultry and horses but has not killed a human here since 1989.

There is worry that this might change if controls are hobbled.

Tiny Maryland had the nation's fifth-highest incidence of malaria -- 63 cases in 1995. It's an imported disease now, but officials fear Maryland's Anopheles quadrimaculatas mosquitoes could become carriers if they bite infected travelers.

Authorities also are monitoring the tiger mosquito, an increasingly common Asian intruder that can transmit both encephalitis and dengue fever; and Aedes aegypti, the yellow fever mosquito that killed hundreds of Baltimoreans in the early 19th century.

So far, "We've been very fortunate," said Cyrus Lesser, mosquito control section chief. But "we're feeling we have less and less tools to do the job all the time."

Lesser is not asking to bombard more wetlands with more powerful chemicals. "Pesticides should not be, and never were, the only answer to mosquito problems," he said.

He prefers the "integrated pest management" and "source reduction" methods. But both are stuck in environmental mud.

The first involves the use of natural predators. In the 1980s, the state stocked many freshwater breeding areas with Gambusia, a sort of guppy that devours mosquito larvae. The DNR objected, worried the fish might eat, or out-compete, frogs and salamanders.

Today, the Gambusia program is down 80 percent, limited to man-made wetlands and storm-water runoff ponds. Where the Gambusia can't be restocked, larvicides are applied five or six times a season.

Source reduction means ditching marshlands to create deeper water and ponds where native fish can live and eat mosquito larvae. In the 1980s, the state was ditching 1,000 to 2,000 acres a year, curbing bugs there for as much as 20 years.

Since 1991, DNR has opposed ditching in pristine marshland. Roland Limpert, a DNR specialist, said changes in hydrology due to ditching could erode the marsh, harming plant life and threatening fauna, including the rare black rail. Ditching is down to fewer than 100 acres a year.

David F. Brinker, a DNR wildlife ecologist, said he is sympathetic. "People are screaming to get rid of mosquitoes, and there's good reason to control them. But there aren't many strategies open to [mosquito control officials]."

In the past, county highway or public works crews sprayed regular routes or on demand. Today, the state does the work. Communities must ask for service, and they don't always get it.

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