Drought dries up mosquito breeding grounds in eastern Mass.
Drought conditions are raising the danger of brush fires and turning lawns and gardens brown, but they may have an upside: Fewer mosquitoes.
Saying weather has dried up or significantly reduced the insect’s usual breeding grounds, several eastern Massachusetts mosquito control programs have put off plans for aerial drops of larvicide in the region’s wetlands, swamps and marshes.
Central Massachusetts, East Middlesex, Norfolk and Plymouth county mosquito control projects cancelled or postponed plans to drop ground-up corn cob treated with Bti, a type of soil bacteria that kills the insect’s larvae, from planes or helicopters.
“That’s the best way to control mosquitoes – to get them in larva state,” said Anthony Texeira, superintendent of the Plymouth County Mosquito Control Project.
Three other programs responsible for mosquito control in Bristol County, Northeast Mass. and Cape Cod do not typically spread larvicide from the air. Directors said their crews distribute it by hand, however, and also have noted unusually low water levels.
“Nature itself is probably going to kill more than we would in a normal spring,” said David Lawson, acting director of the Norfolk County Mosquito Control Project.
Mosquitoes typically lay eggs in stagnant water in warm weather.
While late April could bring rainstorms, some mosquito control officials said it would take considerable rainfall to significantly change dry conditions after a winter with little snow or ice and unusually warm temperatures.
The U.S. Drought Monitor on April 17 said eastern Massachusetts is in a severe drought, with roughly half as much precipitation as normal since January.
“All the grass and the trees are sucking up the water as fast as it comes,” said Jack Card, director of the Northeast Mass. Mosquito and Wetlands Management District.
Some cancellations are rare. East Middlesex had not nixed an aerial drop since 1987, while Norfolk County last put one off because of a plane problem in the 1990s.
“Any of the small areas that are normally wet, you’ll see they’re dry, dry as a bone,” said Stephen Burns, acting superintendent of Bristol County Mosquito Control. “In the deeper part of the swamps, there’s still water and we’ve found some breeding, but around the edges, it’s dry.”
The state is split into nine regions with local programs to control mosquito populations, in part to limit the spread of diseases borne by the insect, such as West Nile virus and Eastern equine encephalitis.
Most programs use hand-distributed larvicide to treat known breeding grounds, answer complaints from residents, dig out areas where water can collect, treat catch basins and in some cases spray from trucks later in the season to kill adult mosquitoes.
But projects vary, depending on the region. Some conduct aerial drops on 10,000 or more acres of wetlands, others are more targeted or the rest lack the large swaths of potential breeding grounds to make airborne treatments cost effective.
While some mainly contend with freshwater mosquitoes, others along the coast are battling the insects in salt marshes.
The state also sometimes carries out additional mosquito spraying.
In some areas this year, mosquitoes that hibernate through winter seemed to emerge early in the warm March weather, some program directors said.
“It was fairly unusual for us,” said Timothy Deschamps, director of the Central Massachusetts Mosquito Control Project. “Those have since pretty much died off.”
The dry spell could mean fewer mosquitoes that typically emerge later in the spring or early summer, some directors said, but it’s hard to predict.
“We’re at the mercy of the weather,” Lawson said. “If it starts raining at any point … the story could change.”
(David Riley can be reached at 508-626-4424 or firstname.lastname@example.org.)