June 16-22 is National Pollinator Week!
Bees are a valuable asset to modern agricultural systems pollinating approximately one third of the crops in our diets. The value added to the agricultural system by insect pollination, mainly from bees, was estimated to be US$190 billion in 2005 worldwide or about 9.5% of total agricultural production. For some crops, like almonds, bees are a vital input to production. In south west China where wild pollinators were decimated by pesticides and habitat loss, apples and pears are now reportedly pollinated by people with paint brushes and clay pots who must visit every blossom.
Both wild and managed bees are in decline in North America. According to the Report on the National Honey Bee Health Stakeholders Conference from 2012, the supply of bees has been steadily dropping in the United States from about 6 million colonies in 1947 to 4 million in 1970, to 2.5 million in 2012. In 2006, these concerns were further heightened after record overwintering losses of 32%. This level of colony loss was well above the 15% lose rate that many beekeepers consider to be acceptable. Since then the winter loss rate has averaged around 30%.[1] Canada has experienced a similar rate of colony loss over this period.
Since 2006, Colony Collapse Disorder, a mysterious ailment, which leads honey bees to vacate their hive before they die, has been of concern to the beekeeping community and is estimated to contribute to about one third of the colony losses in the United States. Honey bee health researchers are still working to determine the cause of CCD but most agree that a combination of factors lead to CCD including environmental stressors and pathogens.
Although CCD has received widespread media attention and has prompted new research into bee health, it is not the primary cause of overwintering loss. The primary hypothesized causes of colony losses are thought to be pests and disease, pesticide exposure and habitat loss.
Pests and Pathogens
Recent research has found varroa mites are the most detrimental pest to honey bees. Varroa mites weaken honey bees and are correlated with increased levels of other viruses such as Deformed wing virus, Acute bee paralysis virus, and Kashmir bee virus. Nosema parasite is another pervasive pest in the United States and has also been cited as a cause of poor colony health. High nosema loads within a colony can lead to infected bees dying prematurely. Research has also demonstrated that there may be a synergistically harmful effect between nosema infection and some pesticides. Deformed wing virus, one of the most prevalent bee viruses in the U.S. has also been found to be correlated with higher overwintering losses. The above are just a few pest and pathogens currently contributing to colony losses in the U.S. There are also concerns that new pests might be inadvertently imported into the country as occurred with varroa mites in 1987.
Are Neonicotinoids to Blame?
Recently, media attention has turned to pesticides as a possible cause of colony decline. In particular, a class of nicotine-derived pesticides, neonicotinoids, have been implicated as a cause of bee deaths. Concern about neonicotinoid contamination of bees lead the European Union to declare a 2-year moratorium on three types of neonicotinoids, clothianidin, imidacloprid and thiametoxam. Recent work found that the pesticides do not appear in the pollen of seed-treated crops, while other studies have found the pesticide in dust emitted during planting. While at high doses, these pesticides can clearly harm bees, there is still a debate whether they are harmful at the low levels of exposure bees would encounter in the field.
Loss of Habitat
Other factors of concern affecting honey bee health include environmental stressors such as poor diet and lack of plant diversity. The loss of natural area in the United States result in diminished food availability and nutritional diversity for wild and managed bees. High grain prices have caused over 10 million acres of CRP lands to be converted back to crop production since 2009. This trend is troubling because research has found that honey bee colonies near greater areas of open land sustain fewer colonies losses and produce more honey compared with colonies located near a greater portion of developed land. Plant diversity from natural areas is essential for maintaining large enough wild bee populations to pollinate cultivated crop. Research on Britain and the Netherlands has also found a link between decreases in the plants that bees pollinate and decreases in the bee populations. Agricultural conservation policies can be adjusted to encourage preservation of pollinator habitat, particularly in areas which use intensive agricultural practices.
Conclusion
As concerns heighten about honey bee loss, several policies have been implemented to protect honey bee populations. The European Union placed a two year moratorium on three neonicotinoids effective December 1, 2013 as a precautionary measure to protect honey bees. In response to concerns about neonicotinoids, the United States EPA is taking steps to mitigate honey bee losses by requiring new labeling on products that contain these insecticides. The U.S. has also recently targeted efforts at protecting pollinator habitat. In February 2014, the USDA Natural Resource Conservation Service announced it will spend $3 million dollarson creating incentives for farmers and rancher to use conservation practices that will promote honey bee habitat in the Midwest. The USDA APHIS also has been continuing efforts to monitor pest and diseases effecting honey bees in the U.S. These efforts are intended to protect against importation of foreign pests. Many researchers fear that the steps being taking to protect honey bees are not far reaching enough. More work is needed to craft policies to protect honey bees, particularly as new research emerges further pinpointing the primary causes of colony losses.
[1] A Bee Informed Partnership (hyperlink: http://beeinformed.org/) survey found total colony loss over the winter to be 23.2% in 2013-2014, 30.5% in 2012-2013, 21.9% in 2011-2012, 30% in 2010-2011, 34% in 2009-2010, 29% in 2008/2009, 36% in 2007-2008, and 32% in 2006/2007.