Earlier this year, Best Food Facts received questions about honey bees and pollination. Dr. Dennis vanEngelsdorp said one in every three bites of food you eat is pollinated either directly or indirectly by honey bees. He said there can be a balance between modern agriculture practices and a thriving honey bee population.
But what about Colony Collapse Disorder? To follow up on our earlier post, we reached out to Dr. Dennis vanEngelsdorp, Assistant Research Scientist, Department of Entomology, University of Maryland, and Meghan McConnell, Faculty Research Assistant, University of Maryland.
Dr. Dennis vanEngelsdorp
What is Colony Collapse Disorder?
Dr. Dennis vanEngelsdorp: "Colony Collapse Disorder, or CCD, is a term applied to honey bee colonies that died or are dying with a very specific set of symptoms. These symptoms include the rapid loss of the adult bee population with the absence of dead bees in and around affected colonies. During collapse, the queen is present and the last remaining bees in the colony appear to be young. Hives of dead colonies have sufficient food reserves and, when abandoned, there is an apparent delay in both robbing of food stores from neighboring hives and kleptoparasitism (a form of feeding in which one animal takes food from another that has already caught or collected the food) from common hive pests like wax moths and small hive beetles. In addition, bee samples from colonies suffering from CCD do not have significant parasite and disease loads from common bee pests."
Meghan McConnell: "Colony Collapse Disorder is a phenomenon when the worker bees of a hive die while the queen bee and the brood are still surviving in the hive. There are usually few signs of the deaths in or around the hives, leading researchers to believe the deaths occur while the worker bees are foraging. The hives usually have adequate honey and pollen reserves, so food supply does not seem to be the issue. Other symptoms may include delayed invasion of hive pests that would usually take over a hive once it becomes weak, or robbing from other hives."
What are the causes of Colony Collapse Disorder?
Dr. Dennis vanEngelsdorp: "Determining the cause of CCD has been the focus of work by many scientists. The growing consensus is that CCD is not caused by a single, definitive cause. It is obvious that CCD colonies are ill. When compared to healthy colonies, CCD colonies are co-infected with many different pathogens. They are commonly suffering from multiple infections with multiple disease organisms including viruses and fungi. While high disease loads may explain the symptoms of CCD, what remains unclear is why CCD-suffering colonies are so susceptible to disease. Three main areas have been explored as likely culprits: (1) a new undetected disease or more virulent strain of an existing bee disease; (2) pesticide exposure; and/or (3) nutritional deficiencies."
Megan McConnell: "Researchers have theorized a few reasons why CCD happens.
"From the EPA:
- increased losses due to the invasive varroa mite (a pest of honey bees);
- new or emerging diseases such as Israeli Acute Paralysis virus;
- the gut parasite Nosema ceranae, a possibly more virulent strain of Nosema;
- pesticide poisoning through exposure to pesticides applied to crops or for in-hive insect or mite control;
- bee management stress;
- foraging habitat modification;
- inadequate forage/poor nutrition; and
- potential immune-suppressing stress on bees caused by one or a combination of factors identified above."
Is agriculture causing Colony Collapse Disorder?
Megan McConnell: "It would be incorrect to say that agriculture is the cause of CCD, but it could be contributing to several of the suspected factors listed above, for example:
- bee management stress - it's possible that transporting bees to pollinate different crops around the country could contribute to hive stress, lead to a decrease in proper nutrition, and could expose bees to many diseases by being collocated in areas with many other pollinating colonies.
- foraging habitat modification - agriculture has been increasing the amount of farmed land and sometimes at the loss of many acres of land that would have provided natural forage for bees.
- inadequate forage/poor nutrition - having one type of forage limits diet diversity so bees could be missing some types of important nutrients.
- new or emerging diseases such as Israeli Acute Paralysis virus and possibly a more virulent strain of the gut parasite Nosema (N. ceranae).
- pesticide poisoning - agriculture contributes heavily to pesticide exposure risks.
"Scientists around the country, with help from beekeepers, are researching what is happening in the hive and around the hive when beekeepers report significant losses. Experiments are also being done to see if chemicals have an effect on bee vitality. Although the impact of agriculture on bees may not be clear, the effect that bees have on agriculture is huge! When CCD was first reported in 2006-2007 the loss to the agricultural economy was projected as $12 billion and it is now estimated at over $15 billion. Bees play a highly critical role in pollinating many foods that we eat. Beekeepers are still reporting unexplainable losses, so this problem and the threat to food security are still unsolved."
Can there be a balance between pesticide use and a healthy honey bee population? (Answer from our previous post.)
Dr. Dennis vanEngelsdorp: “Yes, there can be a balance. We need to make sure that we have bee forage. There’s a growing consensus that farmers should always have meadows so that they don’t plant straight acreages of corn or soybeans. We have to make sure that we have pollinator strips within the boundary, so that we have healthy bee forage. It’s pretty clear that if bees get good nutrition, they’re able to survive a lot of insult, and so dedicating certain portions of the land to pollinator habitat is a good idea.
“Modern agriculture requires some pesticide use, so I don’t think we need to get rid of pesticides altogether – I just think judicious and careful use is important. It’s pretty clear that things we don’t think are harmful to insects, like fungicides, probably have a negative effect, so we probably need to have some regulation on what we spray so that we’re not spraying plants when they’re flowering. We just need some common sense rules like that, as well as making sure we have adequate bee habitat. I certainly think there can be a balance; I just think it has to be a multi-pronged and comprehensive approach."