The sun begins its descent toward distant pines as Paul Nuwer taxis the white, twin-engine turboprop plane onto Runway 3-4 at Cambridge Dorchester Municipal Airport.

Nuwer revs the engines to 42,000 rpm, releases the brake and accelerates the aircraft to the north end of the runway. When the speed tops 100 mph, he pulls back the control yoke and the plane begins its climb to a layer of scattered clouds hovering at about 3,000 feet.

The scene is reminiscent of a flight by a corporate aircraft carrying executives to a meeting. But Nuwer was piloting in the state's newest weapon in the aerial war against mosquitoes, including those that carry the West Nile virus.

The 35-foot-wingspan Beechcraft King represents an important step forward because it can fly at night, when mosquitoes are most active, said Cy Lessor, chief of mosquito control at the Maryland Department of Agriculture.

"This is when we can be the most effective, do the most damage," he said.

Lessor said the aircraft used previously - a single-engine Piper Aztec - was not designed for nighttime flying.

The state bought the Beechcraft for $765,000 from a Virginia company that had been using the aircraft for contract mosquito spraying in Florida, Colorado and North Dakota.

On the recent flight, which lasted 55 minutes, Nuwer flew toward Baltimore, where he sprayed about 12,000 acres of Hart-Miller Island in the Chesapeake Bay. He said about 75 percent of the spraying is usually done over the marshlands of the lower Eastern Shore, a hotbed of mosquito activity.

According to the Maryland Department of Health and Mental Hygiene, there have been 125 cases of West Nile virus in the state since 2001, resulting in 18 deaths.

There was a sharp decline in the number of cases last year. Only 16 cases were reported and none was fatal, compared with 73 cases and eight fatalities in 2003.

Weather conditions - including lower temperatures and less rain - were thought to be factors in the drop-off.

This year there has been one confirmed detection of mosquitoes carrying the virus. That came from a mosquito pool collected last month in the Silver Spring area of Montgomery County.

Nuwer, a 47-year-old former crop duster who lives 12 miles from the Cambridge airport, said: "This has been a very unusual year for mosquitoes. They have been very scarce.

"This is my seventh year flying for the state and I can't remember going up fewer times. I usually fly four or five of every seven days. So far in August, I've only gone up two nights," he said last week.

He attributed the decline to rains on the lower Eastern Shore that have fed enough water into the marshlands to allow minnows to feed on the mosquito larvae.

"But that could all change next month or even next week," he said. "September is usually a very bad month for mosquitoes. Things could get real crazy real quick."

With its new aircraft, the Agriculture Department is better prepared than in the past.

"The main thing the new plane does is allow us to fly when the mosquitoes are most active. This is the half-hour before sunset and throughout the night until sunrise," Lessor said. "We couldn't do that with the other plane."

Flying the previous plane,