Wellesley Biologist Talks with the CBC about Threats to Honey Bees’ Survival

February 20, 2019
A professor holds a tray of bees outside.

Heather Mattila, associate professor of biological sciences at Wellesley, discussed the value of honey bees and threats they face in a recent radio interview with Canadian Broadcasting Corp. (CBC) News. She was in Canada advising the beekeepers association in her hometown of Thunder Bay about how to keep their colonies healthy. 

“We have a huge volume of crops that require a lot of pollinator visitations in order to make good yields of nice, healthy food, whether it’s fruits or vegetables…anything that comes from plants,” said Mattila.

But for all their value to farmers—and consumers—honey bees face multiple threats, she said. One danger is the pesticides and fungicides used by growers.

“A lot of pesticides are very persistent and even systemic—meaning it is sprayed on one part of the plant, it gets soaked up, and moves its way into the plant’s flower,” said Mattila. A bee who comes into contact with the pesticide can carry it back to the hive, she said, where it can “wreak havoc within this hive, and that’s happening across North America.”

Recently, researchers have found that some pesticides previously considered safe for bees were harming adults and larvae during their migration to the almond tree groves in California’s Central Valley. This happens when multiple pesticides are combined in the field.

Mattila, who maintains 25 beehives on Wellesley’s campus each summer, said pesticides are often tested for toxicity one chemical at a time, but not in combinations. 

“What researchers are trying to show now is that many of these pesticides are quite persistent in the environment, so their lethality builds over time, and that untested combinations of pesticides can have serious effects on pollinators,” said Mattila, in an email. “Some of these effects include loss of orientation, poor learning, and a reduced ability to fight disease. Chemical stresses on pollinators are of particular concern because they are linked so tightly with the production of food for human consumption.”

Another threat, said Mattila, is the introduction of predatory insects to North America. A particular danger is the varroa mite, a parasite introduced to Florida in the mid-1980s, she told CBC News.

“The varroa mite is probably the worst parasite that we know of that attack bees,” said Mattila. She described the mites as being like tiny vampires that bite into bees, particularly their larvae. “They like to attach to growing, young bees, the babies of the colony, feeding on nutrients within the bee and transferring viruses to the bee.”

A third threat is winter weather. Honey bees survive on the honey they create and store in their hives in the summer months. When the bee population drops or becomes weak, honey production suffers.

“If the supply of honey is not good enough because the hive has been weakened in the summer …it’s very likely that they will not have enough food to survive the winter,” she said.

On a broader scale, Mattila said, honey bee health is a barometer for insect health. “Failing honey bee health is a canary in the coal mine,” she said. “Several recent studies, from places such as Germany and Puerto Rico, suggest that insect numbers are in severe decline, like has been closely observed for honey bees and other pollinators for over a decade now.”