Massachusetts' wild bumblebees could be at risk even from low environmental levels of neonicotinoid pesticides, according to a new study.

Researchers from Worcester Polytechnic Institute have found that queen and male bumblebees, who are essential to the formation of bee colonies, are particularly vulnerable to neonicotinoids. The study, published in the open-access scientific journal PLOS One, is the first granular look at how these pesticides affect individual queen and male bees.

"As our bumblebees and other native pollinators disappear, so too will our native flowering plants and the animals that use them for food, shelter, and nesting sites," study co-author Robert Gegear said in a statement. "We need to understand all the factors that are contributing to the decline of wild bees, but the evidence is mounting against neonicotinoids in agricultural and urban areas. Because neonicotinoids are readily translocated from the soil to the nectar and pollen of wildflowers growing in these areas and can persist in the environment for long periods of time, they pose a potential hazard to wild bumblebees at every stage of their annual life cycle."

Gegear, an assistant professor of biology and biotechnology, wrote the study with WPI PHD candidate Melissa Mobley.

Each fall, newly spawned male and queen bees leave their wild colonies to mate. Queen bees then find a place where they can survive the winter, staying there as their original colonies die off in the cold. In the spring, they emerge, nest and lay eggs, starting a new colony.

It is that delicate cycle that may be at risk from neonicotinoids, the study says. Gegear and Mobley's research found that while worker bees can survive the low levels of pesticide bees may encounter in the real world, males and queens suffer increased mortality rates.

It is a potential harm missed by previous research on bees, which has largely focused on how neonicotinoids affect managed honeybees kept by humans to use for pollinating crops, Gegear said.

"All of these vulnerable points get missed when you focus on bees in an agricultural context," Gegear said in an interview.

The fate of American bees became a national cause for concern in 2006, when beekeepers and scientists noticed the widespread and unexplained loss of honey bee colonies -- known as Colony Collapse Disorder. Managed honey bee colonies saw loss rates of over 30 percent in the winters of 2006 and 2007, according to the Bee Informed Partnership, a USDA-funded research coalition -- well above acceptable rates of about 15 percent.

Loss rates dropped to the mid-20s, but remained above normal levels. And in 2017-2018, rates spiked about 30 percent again, according to preliminary results from Bee Informed.

The mysterious nature of the colony disappearances drew headlines and outcry from environmental groups, who warned that the loss of pollinating honey bees could pose a threat to the American agricultural ecosystem.

Researchers posed a number of theories about the cause of Colony Collapse Disorder. While parasites and diseases are largely responsible for annual bee deaths, researchers questioned whether a new class of insecticides called neonicitinoids were causing unintended harm to bee populations.

The "Beepocalypse" warned of by breathless media reports has not come to pass for honey bees. Overall managed honey bee populations have rebounded since the mid-2000s, largely due to efforts by beekeepers in the face of continuing colony losses,.

But while Colony Collapse Disorder has largely subsided, die-off rates are still high, Science News reported earlier this year. And that recovery has only been measured for bees kept by humans, leaving the fate of wild bees uncertain.

Those wild bees -- bumblebees and other species who pollinate native plants, rather than tended crops -- are the focus of Gegear and Mobley's research.

The problems facing honey bees are an economic rather than existential problem, Gegear said, with the most likely negative effects being a rise in food prices as the cost of pollination rises for farmers.

But for some of Massachusetts' native bees, the die-offs could could cause extinction. Geager, who has personally surveyed bee populations across much of the state, has found that two of the 11 bee species historically living in Massachusetts are likely no longer present. Another four are in decline, while the rest are stable or increasing in population.

And while farmers are concerned with the raw numbers of workers available to pollinate crops, the state's environment has more specific needs, Gegear said. Wild bumblebees are a keystone species whose pollination habits maintain ecological diversity. And disruptions to those species could ricochet up the foodchain, affecting herbivores who feed on pollinating plants and the predators who eat those animals.

"There are cascading negative effects that ripple throughout the ecosystem," Gegear said. "I don't think people realize when we see birds going extinct, it ultimately could come down to pollinators."

Gegear views his study as evidence of the real-world harms of neonicotinoids, saying that when used on crops, lawns or flower beds, the pesticide can linger in the soil for years and contaminate wildflowers used by wild bees.