Farming Magazine - December, 2009

COLUMNS

Small Livestock: European Honeybees and the CCD Puzzle

By Diane Wells

If we define livestock as animals raised and kept for home use or for profit, European honeybees could be considered as such—and there’s certainly no argument that they’re small. So, we’ll cover honeybees in this column every now and again. I am a beekeeper, and I know a growing number of you are either beekeepers or interested in becoming one. I also know at least a few of you would rather dog paddle through a manure pit than stick your nose in a nest of 40,000 stinging bees. It’s understandable. However, you may still be interested in the creature that plays such a considerable role in the success of our country’s agriculture. They pollinate at least 130 crops that go on to produce roughly $15 billion worth of vegetables, fruits, nuts and forage.

If you read, listen to the radio or watch the television, though, you know European honeybees have been having a particularly rough go of it over the past few years. Although it’s not unusual for a U.S. beekeeper to lose up to a quarter of his or her hives over the course of a winter, many beekeepers lost 30 to 90 percent of their hives during the 2006-2007 winter. What they discovered upon lifting the hive cover was nearly all of the adult bees were gone. Honey, bee bread (pollen that has been packed into a cell and fermented), capped brood and occasionally a queen with a handful of worker bees was all that remained. Dead bees were nowhere to be seen, either in or outside of the hive. Lastly, and what I think is the most intriguing piece of the puzzle, bees from nearby hives were not robbing from the abandoned hive’s unprotected honey and pollen stores. If it was robbed, it was delayed by days, sometimes weeks. Additionally, the invasion of wax moths and small hive beetles, common pests of weak colonies, was significantly delayed. The delay or lack of robbing is extremely unusual.

This phenomenon was first reported by a Pennsylvania beekeeper who was overwintering his hives in Florida. Other beekeepers began sharing their stories and soon enough it became known as colony collapse disorder, or CCD, and federal, state and university researchers began investigating its cause. Initially, the search was for a silver bullet, a parasite, disease, pest or pesticide that would single-handedly explain the losses. However, what researchers began to realize, and what some beekeepers were saying all along, was that it wasn’t likely due to just one bullet, but rather a selection of them that had been building and interacting for some time. For decades, honeybee colonies have been stressed. From the constant barrage of new parasites, pests and diseases and the chemicals beekeepers use to combat them, to pesticides in the environment and the poor nutrition and transportation associated with migratory beekeeping operations. Never mind the overall lack of genetic diversity. How these stressors interacted within the confines of a hive and what synergistic effects they had on colony health was a big mystery. It soon became evident that this was a big jigsaw puzzle. The way I see it, here are a few of the pieces that belong to it.

In the 1980s, the Varroa mite, a honeybee parasite native to Southeast Asia, was detected in a U.S. colony. How long it had been lurking in this country, no one knew. However, since the ’80s, an increasing number of beekeepers have struggled with its control. Today, as one long-time beekeeper glumly told me a couple of years ago, “if you have bees, you have Varroa mites.” It is now considered the primary honeybee parasite and, left unchecked, it will decimate a colony. Not only do the mites feed on adult bees, they also act as vectors and transmit disease.

In 2004, Israeli acute paralysis virus (IAPV) was reported for the first time in the United States (it has since been shown to have been present since at least 2002). Identified in Israel, IAPV is a picorna-like virus that attacks ribosomes, the protein factories in cells. Bees with the virus develop shivering wings, become paralyzed and die. Red flags were raised in September 2007 when a study lead by USDA-ARS, Pennsylvania State University and Columbia University researchers revealed an association between colonies lost to CCD and IAPV. The virus was found in 96.1 percent of the samples from CCD colonies. It was not found in any of the non-CCD colonies.

Meanwhile, folks from the USDA-ARS and the University of Illinois began to study honeybee genes and how their activity levels differed between healthy colonies and those that suffered from CCD. This past August, they published their findings in the Proceedings of the National Academy of Sciences. What they found was honeybees from CCD colonies had a considerable amount of abnormal ribosomal RNA (rRNA) fragments in their guts. Now, rRNA is the central component of a ribosome, and the presence of abnormal fragments means something is wrong. It tells us the ribosomes are under fire and instead of manufacturing beneficial proteins, they’re manufacturing viral proteins. This in turn reduces the honeybee’s ability to cope with infections, poor nutrition and exposure to pesticides.

So, we have a non-native mite that parasitizes honey bees and transmits viruses; a new virus that attacks honey- bee ribosomes; and genetic evidence that CCD-colony ribosomes are being compromised, which in turn compromises the insect’s ability to cope with stressors. Whether these pieces of evidence form the corner, edge or heart of the puzzle, no one yet knows. Incidentally, migratory beekeepers tend to suffer the greatest losses from CCD, from 50 to 90 percent. For many, this is another puzzle piece, an indicator that trucking boxes of bees around the country every year may not be as harmless as once thought.

The percentage of colonies lost to CCD each winter appears to have stabilized: 36 percent in 2007-2008 and 30 percent in 2008-2009. For the Northeast, the most significant losses have occurred in New York, Pennsylvania and Connecticut. Vermont and Maine appear untouched. Why? That’s one of many puzzle pieces we still need to find.

The author, a brand new contributor to Farming, is a biologist who lives and farms in Vermont’s Northeast Kingdom. Comment or question? Visit www.farmingforumsite.com and join in the discussions.