bioGraphic Produced by Louie Schwartzberg April 25, 2017
A blood-sucking mite is wreaking havoc on honey bees - but scientists have discovered a surprising new way to fight back.
A decade ago, honey bee populations around the world began declining at an alarming rate. In the early years of this trend, beekeepers lost 60 percent or more of their hives to a mysterious phenomenon that came to be known as “colony collapse disorder” (CCD). In each of these cases, worker bees simply disappeared, and it doesn’t take long for a colony to collapse without workers to provide food and to care for the young. Although this trend seems to have leveled off somewhat in recent years, the current average rate of 30 percent annual mortality is still nearly double the average rate reported prior to 2006.
Honey bees (Apis mellifera) are native to Europe, western Asia and Africa, but have also been introduced to many other parts of the world to serve as pollinators of agricultural crops. Today, honey bees pollinate one-third of all the crops we consume—nearly a thousand varieties in all—and are by far the world’s most important and economically valuable pollinators for commercial agriculture. In the U.S. alone, their annual value is estimated at $5–14 billion.
Since the first reports of dead and dying honey bee colonies began to stream in, scientists have scrambled to determine the cause, or causes, of CCD. One threat in particular stood out as a major cause of honey bee declines: varroa mites (Varroa destructor). These tiny parasitic arachnids weaken adult and juvenile bees by sucking their blood. They also transmit a number of viruses that can spread throughout a colony like wildfire. To make matters worse, the mites reproduce quickly and, because of this, can rapidly evolve resistance to traditional chemical pesticides.
While many scientists have continued to search for causes of honey bee declines, others have turned their attention to developing new, more sustainable solutions to these threats. One of the more surprising and promising of these strategies is the use of compounds produced by a widely-distributed mushroom (Metarhizium anisopliae) that is known to parasitize a number of different insects. Researchers from Washington State University have found that spores and extracts from this mushroom are particularly toxic to varroa mites but—in low doses—leave bees unharmed. In fact, bees in hives treated with Metarhizium tend to be much healthier and live longer than those in untreated hives. While large-scale trials are just now being implemented, early results suggest that a common mushroom may hold the answer to at least one major driver of honey bee declines.