Ample winter and spring rains are producing a bumper crop of mosquitoes, and state officials are on alert for any breakout of diseases transmitted by the insects.
Scientists say mosquito season is running two weeks earlier than normal after a mild winter and rainy spring. Complaints are up significantly, after several years of drought.
"This year is just starting up with a bang," said Cy Lesser, Maryland's chief mosquito fighter.
Lesser, director of the Maryland Department of Agriculture's mosquito control division, said officials' concerns are heightened by last year's outbreak of West Nile virus, which can be spread by a common domestic mosquito.
Officials say there is no reason for public alarm, but they have stepped up efforts to identify outbreaks of West Nile virus, which was linked to seven deaths from encephalitis in New York last year.
Gov. Parris N. Glendening announced last week that the state had set up a phone line for Marylanders to report suspicious deaths of crows, which can be infected by the virus. Last year, a single dead crow found in Maryland turned out to be infected with the virus, but there were no reports of human exposure in the state. This year, there have been no reports of the virus in Maryland.
For the past three years, Maryland's mosquito problems were held at bay -- at least in the spring and early summer -- by dry conditions that interfered with mosquito breeding. But this year, rainfall has been "right around normal to slightly above normal," said Ken Pickering, Maryland's acting state climatologist.
As of May 21, the weather station at Baltimore-Washington International Airport had reported 16 inches of rain, compared with 15 inches in a normal year, Pickering said. Chestertown, on the Upper Eastern Shore, has been the state's wettest station, with 18 inches -- 2 inches above normal, he said.
People in that area are already feeling the sting.
"This year, we have had many calls from the Upper Shore," said Don Vandrey, a spokesman for the state Agriculture Department.
Vandrey said complaints are also running high in Baltimore County, the Lower Shore, Southern Maryland and southern Prince George's and Anne Arundel counties.
"We are getting calls regularly from mosquito-prone areas asking to be sprayed," he said. " 'Asking' would be a polite word."
Vandrey said the state has stepped up its efforts to kill mosquito larvae in the water to the highest level in recent memory. But he said it has confined its spraying of adult mosquitoes to the lower Eastern Shore.
State officials hope the stepped-up effort to control the larvae will reduce the need for spraying -- a practice that tends to draw protests about its environmental effects.
While much of the state's control effort is focused on the Eastern Shore, where the insects rise in vast swarms from low-lying marshes, state officials are increasingly concerned about a surge in urban mosquitoes.
These new gangs of street mosquitoes include a bloodthirsty imported species that bites at any time of day, can breed in an upturned bottle cap and has staked out Baltimore as part of its turf.
The Asian tiger mosquito is thought to have been imported from the Far East to south Texas in a shipment of tires during the early 1980s, said Adam Richman, an entomology professor at the University of Maryland, College Park.
Richman said reports suggest the Asian mosquito might be crowding out a more familiar species that typically strikes in the evening.
"They tend to be biting all the time. That's what's really problematic about them," he said. "They're aggressive. They're really hard to swat."
Scientists are unsure how much of a threat the Asian mosquito poses to human health. Lesser said it is associated with such diseases as dengue fever and Eastern equine encephalitis, but Richman said it has not been shown to be a serious threat.
State officials said the West Nile virus hot line has received 70 calls with reports of dead birds. None has been found to be infected. Dr. Clifford Johnson, the state public health veterinarian, said it would likely be summer before mosquito populations are large enough to start transmitting the virus.
Officials are advising Marylanders that the best way they can combat the threat is to eliminate pools of standing water around their homes where mosquito larvae can develop.