Multiple threats must be addressed

In 2007, the U.S. Department of Agriculture (USDA) formed the Colony Collapse Disorder Steering Committee to address an unexpected and alarming threat to American agriculture–the soaring number of collapsed honey bee hives.  Colony collapse disorder (CCD) is believed to have complex and sometimes interacting causes, including several directly related to environmental law and regulation (e.g., the use of pesticides and the expansion of land to grow corn used in ethanol).  In October 2012, the CCD Steering Committee hosted a 3-day conference in which stakeholders from many areas shared their ideas on why CCD is a significant threat and its potential remedies.   This article summarizes the current knowledge on CCD as voiced by many experts during the conference.

Dwindling forage areas

It is well recognized that colony decline results at least in part from diseases caused by viruses, parasites, and bacteria.  While the sources of the diseases are well understood, ways to prevent them are either less clear or difficult to implement. 

It is also accepted knowledge that bee colony nutrition is suffering because of shrinking foraging areas, which farmers are converting to more profitable use.  While the corrective action here is obvious–restoring forage areas–experts at the conference said that it has been difficult to convey to farmers the need for foraging areas for bees and then persuade them to undertake best management practices (BMPs) to preserve the habitats bee colonies need to survive and thrive. 

Agricultural pesticides also harm bees.  Accordingly, proactive communication between farmers who use pesticides and beekeepers will expedite the movement of bee colonies before pesticide application begins.  But this communication does not appear to be occurring at the needed levels.  As explained by experts at the conference, bees are critical pollinators for some crops, but not for others.  In the latter cases, farmers who need to quickly treat for pests may not have the time or motivation to work with beekeepers on ways to protect bee colonies. 

Pollination

According to the USDA, an estimated one-third of all food and beverages are made possible by pollination, mainly by honey bees.  In the United States, pollination contributes to $20 to $30 billion in agricultural production annually.  Crops dependent on bee pollination include apples, berries, cantaloupes, cucumbers, and alfalfa.  But there is no more striking example of this symbiosis than the relationship between bees and almond crops in California’s Central Valley.  California farmers grow about 80 percent of the global almond supply on over 700,000 acres, and the demand for almonds is growing.  Currently, 1.5 million to  2 million bee colonies are now needed to cultivate the California almond crop, and bees are now transported into the state to supplement the resident population.  

Considering the importance of bees for agriculture, the proportions of CCD have been frightening.  Between 2007 and 2011, overwinter losses for commercial beekeepers ranged from approximately 28 percent to 33 percent.  The reported rate of loss for the winter of 2011–2012 was 22 percent.  Even with the decline, overall losses exceed the historical rate (approximately 10 percent to 15 percent), and beekeepers have been reporting higher losses again for the 2012–2013 winter.  Overall, since 2006, an estimated 10 million beehives at an approximate current value of $200 each have been lost; the total replacement cost of $2 billion  has been borne by beekeepers alone. 

Varroa destructor

Diseases affecting U.S. bee colonies include the gut pathogen Nosema; American foulbrood, of which several strains have shown resistance to antibiotics in recent years; and European foulbrood, which is occurring with more frequency in U.S. bee colonies.  But, according to USDA’s conference report, the parasitic mite Varroa destructor is the pest most associated with CCD.  The Varroa mite was first detected in the U.S. in 1987.  Research indicates that Varroa mites contribute to CCD by both feeding on developing and adult bees and compromising the bees’ immune systems, thereby serving as transmitters of viruses that can kill bees.  Varroa has shown resistance to the standard synthetic pesticides.  In addition to Varroa, arthropod pests, particularly the small hive beetle, present significant risks to hives.

Nutrition has a major impact on individual bee and colony longevity.  Undernourished or malnourished bees appear to be more susceptible to pathogens, parasites, and other stressors, including toxins.  According to beekeepers and researchers, land-use patterns have changed to an extent where there is less forage available for honey bee colonies.  Also, the use of modern weed control methods in agriculture, forestry, and state land management has reduced availability of the weeds that once provided valuable nutrition to bees.

Bee colony exposure to pesticides has been documented and is a primary concern.  Researchers note that exposure to any one pesticide is rarely enough to kill bees.  But exposure to a range of pesticides over time also occurs, and currently there is limited understanding of the extent to which bees are exposed to pesticides.  Laboratory testing has provided some useful data, but researchers are hesitant to apply laboratory observations to the ways bees contact pesticides in the field and how pesticides are exchanged between bees.

Also, current breeding practices appear to be falling short of the level needed to significantly improve the genetic diversity of bees. 

Needed actions

In conference work groups, researchers stated that the following actions should be taken to better understand and stem the loss of U.S. bee colonies. 

• Pathogens and arthropod pests
  • Conduct additional research to determine the basis for tolerance/resistance by bees to pathogens and arthropod pests.  Recommendations include developing a rapid-turnaround standardized sampling method for different disease/arthropod pest symptoms.
  • Develop new control measures for pathogens and arthropod pests, including new chemical approaches, traps, and bio-control.
  • Monitor for resistance to arthropod and pathogen pests.
  • Improve monitoring, including conducting surveys of as many pathogens and arthropod pests as possible and using the survey data to develop prediction models of bee mortality.
  • Develop rapid response plans that include quarantines for newly introduced exotic pests and/or BMPs that may include destruction of infected/infested colonies.  One conference participant said it was essential that the plan include guaranteed financial compensation so that beekeepers could restock destroyed colonies with clean colonies.
• Pesticides
  • Amend pesticide labels to improve applicator understanding of bee-safe practices.  One conference participant noted that when EPA’s pesticide registration process includes uncertainties about potential effects of a pesticide on bees, the burdens are unfairly borne by the public. The EPA should, therefore, do a better job of accounting for potential risks before registering a pesticide, stated the participant.
  • Improve reporting of bee kills.  Certain obstacles need to be overcome here.  For example, participants noted that some beekeepers are reluctant to report incidents for fear of damaging relationships with growers or attracting government inspectors.
  • Apply pesticides with short residual toxicity at night to reduce the risk of bee exposure to pesticides.
  • Make more extensive use of crop advisors to educate U.S. growers on the effects their activities have on bees.  The need to first educate crop advisors on bee protection practices was expressed.
  • Encourage efforts such as those by CropLife America, which includes sessions on pollinator issues in their annual meetings.
  • Appoint a national coordinator to facilitate communication between parties.
  • Establish suitable foraging areas so that bees do not move into pesticide-treated areas.
• Genetics, breeding, and biology
  • Work group participants noted that long-term, sustainable solutions for honey bee health and productivity issues would most likely derive from increased genetic diversity, which improves the disease resistance of bees and worker productivity.  Recommendations included:
  • Select for breeding colonies that show high levels of hygienic behavior, which improves resistance to Varroa mites and diseases such as American foulbrood.
  • Develop bee strains that contain certain traits that control infestation.  For example, some strains exhibit grooming behavior wherein mites are physically removed from infested adult bees or killed by chewing.
  • Promote selection of honey bee strains, particularly the Russian honey bee, which have an innate resistance to parasitic mites.  Commercial production of the Russian honey bee strain (approximately 2,000 queens per year) is low compared to the current production of 1 million queens per year in the U.S.
  • Develop a repository wherein honey bee germplasm (semen) would be cryo-preserved.  A germplasm repository would allow for the preservation of top-tier genetic resources from the current U.S. honey bee population.
• Tech teams
  Workshop participants also proposed establishment and support of regional tech teams in the U.S. to assist beekeepers.  The system discussed was based on a model in use in Canada and another currently operating in California to assist queen breeders. The concept of the tech team is that a group of trained individuals work in the field with beekeepers to assess stocks and provide information that would inform management decisions to assess and breed bees (in the case of queen producers) and maintain colony health. The approach represents a new field-active model and a tool for action at the interface of science (applied research) and industry (informed management). The model calls for a fee-for-service approach that will make the tech teams self-supporting within a few years.
  In addition to assisting the industry with the implementation of research findings such as genetic improvement or colony health, tech teams would provide a means for capturing data on current honey bee populations that can be used for epidemiological analyses or breeding through identification of high-quality stocks.
  A new tech team is starting up in the Midwest as part of the Bee Informed Partnership (http://beeinformed.org), and there is strong interest in developing a tech team for the southeastern United States.

The conferees also noted that there are few diagnostic laboratories in the U.S. to support beekeepers that wish to submit samples of their bees for determination of pathogen and parasite loads.  Participants therefore discussed the need to establish one or more diagnostic laboratories tasked with providing rapid turnaround analyses of such pathogens as Verroa.  These laboratories could also be useful in evaluating submitted stocks for genetic markers for trait selection as that technology becomes available.

Click here for the USDA’s Report on the National Stakeholders Conference on Honey Bee Health .

William C. Schillaci
BSchillaci@blr.com