Bumblebee numbers falling

The fuzzy, buzzing bumblebee, harbinger of spring, pollinator of plants and perennials, has been suffering declining populations in the Northeast, according to entomologists.

Ted Bruetsch, professor of entomology at SUNY Cobleskill, said fewer bumblebees have been showing up in his students’ insect collections.

“Every spring semester, my entomology class is required to submit an insect collection and almost every year there were lots of bumblebees in the collection,” he said. “But this year there were nowhere near the numbers there used to be. Moreover, I haven’t seen many bumblebees this year myself.”

He said studies by bee experts have revealed a significant drop in some bumblebee populations over the years.

Bruce Danforth, an entomology professor at Cornell University, whose specialties include the conservation of bees, noted that his research has corroborated an earlier study revealing the widespread decline of certain bumblebee species in regions of North America.

He noted that a team of entomologists in 2010, led by Sydney Cameron at the University of Illinois, analyzed the geographic distribution and genetic diversity of various species of bumblebees by examining museum collections of bee specimens and comparing the data with current sampling surveys of similar geographic ranges.

“For example, Cornell University’s bee collection has data that goes back to 1860 and gives us a picture of which bees were in the area in the 1860s up until the present,” he said.

Cameron and her researchers found declining populations in several of the bumblebee species.

Species not found

“There are a number of bumblebee species you can’t collect anymore,” said Danforth. “We’re not picking them up in modern collections. So that’s the best data we have that bumblebees are in decline.”

One species is the rusty-patched bumblebee, an eastern bee with a small rust-colored patch in the middle of its abdomen.

The Xerces Society for Invertebrate Conservation has petitioned the U.S. Department of the Interior to list the rusty-patched bumblebee as an endangered species.

In her petition letter, Sarina Jepson, the society’s endangered species program director, noted the “rusty-patched bumble bee was historically common from the Upper Midwest to the eastern seaboard, but in recent years it has been lost from more than three-quarters of its historic range and its relative abundance has declined by 95 percent.”

There may be several factors involved in the loss of bumblebee populations, said Danforth. However, the most likely are lack of genetic diversity and evidence of a pathogen, a parasite, Nosema bombi, that has been inflicting some of the bumblebee species. Genetic diversity helps a species resist lethal pathogens.

“There is a theory that if Nosema is the problem in the North American bumblebee decline, it’s possible it came from Europe when certain species of bumblebees were brought here for agricultural pollination in the 1960s or later.

“And when you move species around the world like that, you have the possibility of transmitting diseases,” Danforth said.

Two other factors that some researchers are exploring are loss of habitat and the introduction of certain pesticides.

“There is some evidence that loss of habitat could be a possibility, and another [possibility is] new novel pesticides which may be causing collateral damage” when pesticide spraying is done in areas where the bumblebee collects nectar and pollen, Danforth said.

“We don’t know what effect those factors have on the major disappearance of some bumblebee species across an entire range, however.”

Though bumblebees are important pollinators for flowers and agricultural crops, he said, “We don’t know yet what effect the decline in their populations will have on the pollination of plants since they aren’t the only bee pollinators. In New York state alone there are about 450 different bee species and a total of about 4,000 bee species in the United States. Bumblebees are a small fraction of them.”

Honeybees decline

Honeybees are a major pollinator of agricultural crops. However, they too have been facing population declines.

According to the U.S. Department of Agriculture, the cause of the decline in the honeybee population, referred to as Colony Collapse Disorder has yet to be determined. The agency’s research service has been leading efforts into possible causes, such as diseases and parasites. Universities and private companies are also engaged in studies to determine the causes of CCD.

“Honeybees are important agricultural pollinators, but they are also highly domesticated,” Danforth said.

“There are a lot of people thinking ‘Oh, the honeybee is in decline so it’s sort of a sign of an ecological disaster.’ However, the honeybee is really a managed pollinator.”

Though the honeybee plays a significant role in pollinating agricultural crops, he added, “It’s not a wild pollinator, so the bumblebees are giving us a much better picture of what’s going on in the natural environment than honeybees are. Since we’re losing some of the bumblebee species, that should be a warning that people need to pay attention to.”