Pesticides, climate change, habitat loss — the list of threats to native pollinators is already pretty long. Now scientists say there’s another danger lurking about: viruses transmitted by farmed honeybees.
When people say, “Save the bees!” they’re usually referring to farmed honeybees, which in recent years have suffered from colony collapse disorder (CCD). And while those bees are incredibly important pollinators for many of the crops we eat — everything from almonds and apples to melons and cranberries — the bees themselves are not native to the United States. Those honeybees, known as Apis mellifera, actually come from Europe.
Native bees, on the other hand, include more than 4,000 species of bumblebees, carpenter bees, mud wasps, and a bajillion other shiny-winged things that most of us overlook. And while those species don’t have to contend with CCD, scientists have thought for some time that diseases may be able to pass from one population to another, says Samantha Alger, a research affiliate at the University of Vermont. But until recently, no one had ever tested whether this suspected germ swap was really happening.
So Alger designed an experiment, and in the summer of 2015, she and her team collected bumblebees and honeybees from nearly 20 sites across Vermont. Some of the sites were within about 1,000 feet of a commercial apiary operation, and some of them were in locations where no farmed honeybees could be detected within more than half a mile. Given what scientists know about honeybee and bumblebee flight distances, this buffer area ensured that there’d be no overlap between the two types of bees.
Alger tested all of the collected bees for the presence of two common viruses that affect honeybees, deformed wing virus and black queen cell virus. If these names sound scary, it’s because they are — for bees and beekeepers, at least. Deformed wing virus, which is spread by a parasite called the varroa mite, stunts the growth of a bee’s wings, rendering them useless, and distorts its abdomen. Infected bees usually survive for only 48 hours, and their bee colleagues often eject them from the hive. Black queen cell virus, on the other hand, can threaten an entire hive by turning all the pupae produced by a seemingly healthy queen into black carcasses.
“What we found was that bumblebees were more likely to be infected when they were collected near honeybee apiaries,” says Alger, who is also a pollinator specialist at the consulting engineering firm VHB.
A closer inspection revealed that these were active infections. So the viruses weren’t just sitting there on the native bumbles’ feet or wings; they were already inside the insects, doing what viruses do: replicating. The wild bumblebees taken from sites where there were more honeybees buzzing around showed higher virus prevalence.
“Then the question was ‘How are these viruses getting around?’ ” says Alger.
To investigate this, the team took flowering plants from each of the sites and tested their surfaces for viruses. Given that viruses are exceedingly small and there are a lot of flowers around, Alger knew she was essentially looking for needles in a haystack. But lo and behold, she found them.
“We were surprised to find a very high proportion of these flowers had bee viruses,” she says.
Even more telling was that all of the flowers tested at sites far away from honeybee apiaries came back negative.
While these data suggest that farmed honeybees are seeding flowers with viruses that wild bumblebees can and do pick up, Alger says to definitively prove it, researchers will need to watch the virus make the leap under controlled lab conditions. And she’s working on doing just that.
But for now Alger’s results, published in June in the journal PLOS ONE, should serve as a wakeup call to regulators and beekeepers alike.
For starters, Alger recommends that beekeepers remain vigilant about varroa mite infestations — to protect not only their bee colonies but also wild ones. Some keepers, it seems, prefer to manage their hives without the chemicals used to treat mites in an attempt to remain “treatment free” — a fine practice, says Alger, unless you have a parasite problem.
“Honeybees are an agricultural livestock animal,” says Alger, who is herself a beekeeper and on the advisory board of the Vermont Beekeepers Association. “Say you’re a chicken farmer and you go and find your chickens are just completely infested with a parasite. What would you do?”
Furthermore, deformed wing virus and black queen cell virus are just two of more than 20 viruses known to infect honeybees. And we still know next to nothing about how those pathogens affect wild pollinators like bumblebees.
Finally, the findings should raise concern about whether apiaries should be permitted near wild areas where endangered species like the recently listed rusty patched bumblebee or yellow-faced bees of Hawaii still roam.
Because so many species of native pollinators are already on the ropes, it’s important that scientists investigate the potential for contagion now, before there’s a devastating outbreak. And if that research also benefits the beekeeping industry by shedding light on how viruses move through the world, then everybody wins.