American beekeepers have spent decades struggling with colony collapse disorder (CCD), which causes bees to mysteriously abandon their hives. CCD has raised concerns not just for beekeepers, but for farmers of all stripes — plus anyone who eats their crops. U.S. honeybees pollinate about $15 billion worth of crops per year, which provide a quarter of all food eaten nationwide.

It comes as unwelcome news, then, that domesticated U.S. honeybee hives reported the greatest winter hive loss since the survey began 13 years ago. U.S. beekeepers lost nearly 40% of their honeybee colonies last winter, according to the Bee Informed Partnership. That follows the trend of declines of the last few years, according to the U.S. Department of Agriculture (USDA). There were 2.69 million commercial honeybee colonies in the U.S. as of 2018, and the survey respondents represent about 12% of the total hives.

Backyard beekeepers lost more colonies over the winter (39.8%) compared to sideline (36.5%) and commercial (37.5%) beekeepers. Backyard, sideline, and commercial beekeepers are defined as those managing 50 or fewer colonies, 51 to 500 colonies, and 501 or more colonies, respectively.

The effects of CCD have always varied from year to year — including a dramatic improvement in 2017 — so the broader significance of this shift remains hazy. Plus, drops in CCD are at least partly due to beekeepers’ practice of splitting hives. This is a normal practice that mimics how a hive naturally creates new colonies, but it also weakens the original hive in the short-term, and may not be sustainable over time unless life starts getting easier for bees in general.

Mite and main

A varroa mite on a honeybee host, captured by a scanning electron microscope. (Photo: Wikimedia Commons)

The causes of CCD are still hazy a decade after its 2006 debut, but research points to a variety of triggers for recent bee declines, including varroa mites — invasive parasites that are wreaking havoc with hives across the country.

Varroa mites are native to Asia, and were first found on U.S. soil in 1987. Aside from killing bees directly, the parasites have a mosquito-like knack for spreading infectious diseases through a hive. They were the No. 1 stressor in 2016 for all beekeeping operations with at least five colonies, according to the USDA, and were reported in 42 percent of U.S. commercial colonies between April and June of 2017. That’s down from 53 percent during the same period in 2016, but it’s not low enough to reassure bee experts like May Berenbaum, head of the entomology department at University of Illinois Urbana-Champaign.

“[I]t’s staggering that half of America’s bees have mites,” Berenbaum tells Bloomberg. “Colony collapse disorder has been vastly overshadowed by diseases, recognizable parasites and diagnosable physiological problems.”

What else is bugging bees

Research suggests residue from the pesticide imidacloprid can be high in pollen and nectar of citrus plants, like this lemon tree. (Photo: Larisa Blinova/Shutterstock)

Varroa mites are still just one of many problems facing U.S. honeybees. While they plagued 42% of colonies in the second quarter of 2017, about 12% of all colonies were stressed by other parasites, like tracheal mites, hive beetles and wax moths. Roughly 4% were stressed by diseases like deformed wing virus, while more than 6% battled problems like bad weather and insufficient foraging. Pesticides, meanwhile, reportedly stressed 13% of honeybee colonies from April to June.

Insecticides are widely sprayed to thwart crop pests, but research has shown broad-spectrum toxins can endanger foraging bees, too — particularly a class known as neonicotinoids. And once a colony loses enough adult bees, it can suffer a downward spiral caused by young bees trying to pick up the slack before they’re ready, essentially growing up too fast.

These problems aren’t unique to managed bees, either. Wild bumblebees are also in decline, possibly even catching diseases from domesticated bees, although lack of visibility means their woes tend to get less human attention. And while much of the focus has been on neonicotinoids, other pesticides pose sub-lethal threats that still imperil bees. A 2014 study found pyrethroids can stunt the growth of young bumblebees, resulting in smaller workers that may be less effective foragers.

In fact, beyond the plight of honeybees, North America’s bee biodiversity is in serious danger. About half of bee species native to the U.S. Midwest have vanished from their historic ranges in the past century, and more than a quarter of all North American bumblebees face some degree of extinction risk. And this is part of a broader trend — according to the U.N., 40 percent of all invertebrate pollinators are on a path toward extinction, including bees as well as beetles, butterflies and wasps.

How to help bees

Purple coneflowers, like these at an urban rain garden in Minnesota, can be a big boost for native pollinators. (Photo: U.S. Fish and Wildlife Service/Flickr)

Bees need all the help they can get, from domesticated honeybees to their many wild cousins. Most Americans might not be able to protect commercial beehives from mites or viruses, but there are still small things almost anyone can do to benefit bees.

Avoiding outdoor insecticides is one option, especially near flowers where bees might forage. And nurturing native plants could be a huge boon for local bees, whether it’s a 1,000-acre prairie or a patch of meadow in your yard. For help planning a pollinator garden, here’s a list of plants that support bees, plus more tips for repaying the pollinators who keep our habitats buzzing.

Editor’s note: This story has been updated since it was published in August 2017.