Bees are the forgotten farmers; they pollinate over 75% of agricultural and flowering crops. The organization “Bees Matter” estimates that “one out of every three bites of food that we eat is made possible by pollinators like honey bees.” Our reliance on bees for food is one reason why the declining western honey bee population has many people worried. This phenomenon is known as Colony Collapse Disorder (CCD). The exact cause of CCD is unknown, but there are common symptoms that provide some clues, including a dramatic loss of adult worker bees, and abundant food stores in the hive that are not immediately eaten by other bees or pests.
In this study, researchers compared diseased colonies to healthy colonies to determine the cause of CCD. They measured colony stress by recording the mass of the bees, protein levels, and bee symmetry and overall appearance. The presence of parasites and pesticides were also investigated for their potential role in CCD.
This study could not pinpoint a single cause, pathogen, or parasite responsible for CDC, but the pattern of CCD-affected colonies was not random. These colonies were found in close physical proximity, suggesting that an infectious agent or common risk factor may be responsible. The authors suggest that the loss of worker bees may be a result of bees leaving the hive to die or becoming sick and not returning. Interestingly, the bees remaining in affected colonies were notably fit, as inferred from overall appearance. Colonies infected with pathogens or parasites were more likely to have CCD, suggesting that prior exposure to a pathogen weakens the colony and increases susceptibility to CCD. Although continuous exposure to pesticides can weaken the bee immune system, the study did not find the presence or abundance of any pesticides occurred more frequently in CCD-affected colonies. Interestingly, they did find that specific pesticides occured more frequently and at higher levels in control colonies in comparison to CCD-affected colonies.
This study highlights several potential risks for CCD, although the exact cause still remains unknown. Studies like this provide important clues about the underlying causes of CCD, which we need to understand so we can design strategies to prevent it.
Summary written by: Catherine Robertson
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[…] numbers is not fully understood (see previous PLoSibilities posts, “To Bee or not to Bee” and “The plight of the honey bee” ). A new study posits an interesting new theory that could explain more about the collapse of the […]