Honeybees are important crop pollinators, but they are disappearing. A U. Mass. researcher says other native bees can be nurtured to pick up the slack.

Jennifer Cutraro

There’s been a lot of buzz around bees lately, and with good reason. Beekeepers across the country have lost up to 90 percent of the honeybees in their hives since last fall—and nobody knows why. This is bad news for U.S. agriculture—many food crops such as tomatoes, apples, and Massachusetts’s largest agricultural crop, cranberries, rely heavily on honeybee pollination. Beekeepers’ colonies have been wiped out in least 24 states, but so far Massachusetts honeybees have been spared.

While many scientists are trying to figure out what’s causing this disappearance, called colony collapse disorder, others are exploring the possibility that bumblebees and other insect pollinators native to North America will do the job of the honeybees—imported from Europe centuries ago—as they bottom out.

One of those researchers is University of Massachusetts entomologist Anne Averill, who is working with the Cape Cod Cranberry Growers’ Association to encourage cranberry farmers to cultivate “bee pastures”: plots of land adjacent to the cranberry bog that have the right mix of plants to encourage bumblebees and other native species to take up residence and grow in population size. It’s an old idea in agriculture, but one that hasn’t been popular until now, she says.

“With the colony collapse problems, people are gaining a new appreciation for how important it is to keep some land for native pollinators,” Averill says.

Bumblebees are efficient crop pollinators and may be able to fill in the gaps left by disappearing honeybee populations.

Establishing bee pastures is tougher than it sounds, she points out. Averill’s goal is to identify flower species that bloom before and after the blooming of cranberry vines, ensuring a steady food supply that attracts bees at just the right time. It’s also important to identify species that won’t become weeds on the bog or compete with the cranberry plants for bees. Averill, along with the cranberry growers’ association, is developing guidelines and species lists for cranberry farmers interested in promoting native bees on their land.

Bee pastures are a good idea, says Brian Wick, director of regulator services with the Cape Cod Cranberry Growers’ Association. “The longer [native bees] can pollinate, the healthier they’re going to be, and that will build up their populations around the bogs,” he says.

Bee census

The first step, though, is to learn more about how much the populations of native bees have shrunk. “There is a worldwide recognition of the decline in native pollinators,” says Averill. “But what’s missing is quantitative data showing how severe this decline is.” Even the National Academy of Sciences has addressed the problem; last fall, it called for improved monitoring of bee populations nationwide, citing their economic and ecological importance.

A better understanding of native bee status will help Averill and her colleagues predict the impact these species can have in pollinating cranberry vines. And it will help researchers build and modify habitats so that they will boost the number of native bees, adds Averill.

To that end, Averill and her collaborators this summer began a three-year project to conduct population surveys of bumblebees and other native pollinating insects on Massachusetts cranberry bogs. They will compare their data with those from a 15-year-old study on the same populations. She and her colleagues are wrapping up their first season of collecting insects on a bog in East Wareham and will spend the fall and winter tallying up the species they found.

In the end, bumblebees and other native pollinators probably won’t take the place of honeybees anytime soon. “Native bees will never replace managed hives; there are just too many blooms to pollinate,” Wick says. “But the natives can play an important role—whatever percentage they contribute to the bloom, that’s a bonus.”