COLONY COLLAPSE DISORDER (CCD)
Entomologists are currently studying the reasons behind the enormous bee die-off happening worldwide. The phenomenon is called Colony Collapse Disorder (CCD), and is characterized by the sudden -- overnight, in some cases -- loss of the vast majority of the hive, leaving a queen, full brood (larvae) cells, and full honey stores behind. In collapsed hives, no dead bees are found -- puzzling scientists and posing a major challenge to the study of the disease. The USDA has been studying the phenomenon since 2009, when it became apparent that Colony Collapse was not something that would disappear on its own.
A recent USDA-sponsored survey conducted by the Bee Informed Partnership has found that the current rate of mortality for bees in managed hives is 44%, up 3.5% from the 2014-2015 year.
Research on the possible causes of CCD is currently ongoing, and there has been progress! Most recent evidence points to a combination of factors as the culprit -– according to the USDA, these factors include “parasites and pests, pathogens, poor nutrition, and sublethal exposure to pesticides.”
Farming in monoculture limits the bees’ diet to one type of pollen for extended periods of time. Think of it as if a human was limited to eating only strawberries for three months -- not very healthy. These malnourished bees are more susceptible to chemical pesticides, parasites, and pathogens.
The most studied chemical culprit is a class of agricultural pesticides called "neonicotinoids." These chemicals are systemic, meaning the plant takes them into its vascular system, and spreads it to all tissues. They are effective after only one application, and affect only invertebrates- meaning they are less susceptible to runoff, and less dangerous to humans, birds, livestock, etc. They're very popular. In theory, the pesticide shouldn't affect bees, who are eating the pollen and nectar, not the plant's tissue. However, studies have found trace amounts of pesticide in pollen grains. Bees bring pollen back to their hives for food - one pollen grain with trace chemicals wouldn't be an issue, but scientists have found that the chemicals accumulate to critical levels within the beeswax.
Bee communication is almost entirely reliant on chemical and physical signals - these chemicals have been shown to alter their foraging behavior, their communication, and their larval development.
The problem with blaming everything on neonicotinoids or another pesticide is that the bees affected by CCD don't show the trademark symptoms of pesticide poisoning - meaning neonics can't be the sole cause.
The combined application of neonics, other insecticides, and fungicides leaves beehives wide open to parasitic infection.
The most dangerous parasite threatening beehives currently is a mite with a descriptive name: Varroa destructor. Commonly known as Varroa mites, these parasites often infect bees before they can even emerge as adults. When a hive is already weakened, a Varroa mite infestation can wipe it out. Other parasites involved in collapsing hives include the small hive beetle, Aethina tumida; and Nosema spp., a microsporidian gut parasite.
Weakened immune systems leave hives susceptible to bacterial and viral diseases as well. Two of the most well known diseases to infect bees are American Foulbrood and Deformed Wing virus. American Foulbrood affects larvae less than a day old, preventing them from surviving until adulthood, while Deformed Wing Virus is transmitted through Varroa mites and prevents the bees from being able to fly.
I heard that cell phones and may have something to do with it, is this true?
Researchers have ruled out cell phones as a potential cause of CCD. The idea that cell phones may contribute to colony losses originated with a study done in the EU in 2010. It suggested that radiation from the towers altered the electromagnetic field of the earth and, in turn, the bee’s homing ability. There is no real evidence that honeybees rely on the electromagnetic field to navigate, and many apiaries that are still experiencing losses are in rural areas where cell phone service is spotty or absent.
Our information is sourced from the USDA's annual reports on honeybee health, USDA's most recent information on the productivity and estimated pollination effectiveness of bees, and from recent peer-reviewed publications.
Emily Erickson, graduate student of Entomology at UC Davis, helped research and write this post.
For more information, check out:
Heid, Markham. "You Asked: Are the Honeybees Still Disappearing?" Time. 15 April, 2015. http://time.com/3821467/bees-honeybees-environment/
Moye, David. "Cell Phones Don't Kill Bees (STUDY)." The Huffington Post. 26 November, 2011. http://www.huffingtonpost.com/2011/05/19/cell-phones-kill-bees-study_n_863019.html
"USDA Releases Results of New Survey on Honey Bee Colony Health." USDA. 12 May, 2016. http://www.usda.gov/wps/portal/usda/usdahome?contentid=2016/05/0114.xml
Wright, Matthew. "Nation's Beekeepers Lost 44% of Managed Hives in 2015-16." Bee Informed Partnership. 10 May 2016. https://beeinformed.org/2016/05/10/nations-beekeepers-lost-44-percent-of-bees-in-2015-16/