WAKEFIELD — Dead bumblebees littered the sidewalk in front of Wakefield’s Saint Joseph School. Some were still dying, while others were found in clusters around trees and shrubs that decorated the front of the school.
One local homeowner reported seeing “hundreds if not thousands” of dead and dying bees over the weekend in an e-mail to the Pollinator Stewardship Council, a group that helps protect bees across the country.
While it is unclear what killed the insects, several beekeepers across the state have experienced similar losses — losing up to 10,000 bees at a time — which they have attributed to pesticide spraying.
At this time of year, communities often spray areas where mosquitoes breed to prevent the spread of mosquito-borne illnesses, such as West Nile virus and Eastern equine encephalitis. The pesticides typically contain toxic ingredients that kill bees and other insects and animals.
Saint Joseph has never sprayed pesticides on its plants or trees, said Alyne Flynn, a school administrator.
But the East Middlesex Mosquito Control Project, which oversees spraying in Wakefield, sprayed sumithrin on residential streets about 2 to 3 miles from Saint Joseph starting at 8:15 p.m. on three evenings last week, said David Henley, the group’s superintendent. The pesticide is also known by the brand name Anvil 10+10.
Henley said that mosquito control sprayed because trappings showed high numbers of mosquitoes, but the group has not identified disease-carrying insects.
Sumithrin is highly toxic to bees, specialists said, and it was sprayed when bees could still be out foraging for pollen. Bumblebees can travel up to 5 miles, so a traveling community could have become infected, leading to the rapid die-off, said Dr. Alex Lu, associate professor of environmental exposure biology at the Harvard School of Public Health.
“Sumithrin is not a good choice for mosquito control, especially in the area with dense population,” Lu said.
State health officials conduct aerial spraying of disease-carrying mosquitoes when they are most prevalent, which is typically in late July or August. The spraying has faced criticism from farmers and beekeepers who worry about the pesticide’s unintended victims.
Beekeepers across the country have also reported dramatic losses to pesticide control, Lu said, adding that bees are needed to pollinate nutritious foods such as apples, blueberries, and strawberries. Bees have been dying off in alarming numbers over the past several years, leaving the nation with too few hives.
“There have been mass bee deaths that have been unexplained,” said Kimberly Klibansky, a beekeeper in Rowley.
Klibansky and her husband, also a beekeeper, both lost whole hives in 2012, about 100,000 bees. “Farmers are going out to their fields and the bees are just gone,” she said. “There’s no evidence of dead bees at their hives.”
Lauren Mangarelli, an 8-year-old student at Saint Joseph, said she noticed many dead bees in the parking lot and in front of the school over the past couple of days.
“It’s kind of weird because I see them everywhere,” Mangarelli said. “It’s freaking me out. They’re everywhere, and we’re barefoot a lot, and I don’t want to step in them.”
Bee activists said local pesticide groups can work with farmers and beekeepers to protect both public health and bee populations by spraying pesticides only late at night when it is completely dark. Local governing bodies and the state can also allow some beekeepers to opt out of having areas near their hives sprayed, they said.
“Bees are the canary in the coal mine,” said Michele Colopy, program director of Pollinator Stewardship Council. “We understand that the public health concerns and protections will always trump concerns for non-target species, and beekeepers realize that, but there are ways we can work together to protect bees from mosquito spray.”