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Beekeeping - Apiculture in Arkansas
Colony Collapse Disorder
Hard Times for Honey Bees
Honey bees are the world’s best known pollinators. These industrious insects
add an estimated $15 billion in increased crop yields each year in the U.S.
There are around 20,000 species of bees in the world, and nearly 4000 species
native to North America, but the European honey bee, Apis Mellifera,
performs more than 80 percent of pollination on most of our commercial crops.
Approximately one third of our diet is directly or indirectly dependent on bee
pollination. This includes the obvious fruits and vegetables, as well as many
nuts, oil-seed crops, herbs and spices, and much of the forage that is needed
for the beef and dairy industries. In addition, bees pollinate a number of
non-crop plants that are vital to wildlife and to the propagation of the plants
themselves. The California almond crop alone requires 1.3 million colonies of
bees each year - approximately half of our Nation’s managed honey bees - which must
be transported into the growing area each spring.
A dramatic decrease in feral honey bee populations began in the 1980s, with
the accidental importation of two parasitic mite species. Since then, the
increasing costs associated with managing honey bees with these mites and other
hive pests, combined with depressed honey prices caused by cheap imported honey,
has caused many beekeepers to quit the industry. Since the 1940s the number of
managed bee colonies in the U.S. has declined from over 5 million to about 2.5
million. With feral bee populations effectively decimated, the need for mobile
pollination services has increased. The current situation affecting managed bees
may result in a pollinator shortage that could become a crisis for agricultural
production.
Beginning in the winter of 2006, beekeepers across the U.S. reported losses
of 50 to 90 percent of their colonies. In many cases the hives had appeared
healthy and active within a few weeks of colony failure. Colonies that survived
this situation often had populations too small to provide effective pollination
or honey production. Losses of overwintering colonies are not unknown, but at
least half of these colony deaths exhibited symptoms inconsistent with those of
parasitic mites or other known diseases. Because the cause of death was
undetermined, the name “Colony Collapse Disorder” (or CCD) was used to describe
the situation.
CCD may not be a new and distinct phenomenon. Large-scale bee die-offs have
periodically occurred in the past. Older literature describes these situations
as spring dwindle disease, fall dwindle, or autumn collapse. In 1975, a
situation termed Disappearing Disease affected a large number of bee colonies in the
U.S. It may never be determined if these historic situations share a common
cause with the current crisis. In the current situation the bee populations do
not dwindle, implying a slow death over time, but the adult population
effectively disappears suddenly, within a few weeks or days. Also the term
disease implies a pathogen is responsible for the condition, which is something
unknown at this point. Therefore, Colony Collapse Disorder is a more appropriate
term for the present phenomenon.
Common symptoms of CCD include: (1) a sudden loss of the colony’s adult bee
population; (2) very few dead bees present in or around the hive; (3) the
presence of a healthy laying queen bee with a small cluster of newly-emerged
attending workers; (4) frames of healthy, capped brood with low levels of
parasitic mites, indicating that the colony was recently vigorous and healthy;
(5) substantial food reserves of pollen and honey, which are not readily robbed
by other active colonies in the vicinity; (6) minimal evidence of invasion by
wax moths, small hive beetles, or other opportunistic hive pests. In colonies
that are actively collapsing, the number of worker bees is insufficient to
maintain the amount of brood present, and the workforce that is present is
composed entirely of younger bees.
Because few dead bees remain in or around the affected hives, studying the
cause associated with CCD has been difficult. By all appearances, the adult
worker bee population simply leaves the hive and does not return. Surveys have
been designed to determine what variables the affected colonies may have had in
common, but much of this data is based on anecdotal reports provided by
beekeepers. Presently, many thousands of U.S. bee colonies are believed to have died
in the past three years, expressing at least some of the symptoms of CCD. The
phenomenon has been reported by apiary inspectors in 35 states, including
Arkansas. Clearly, honey bees across the nation are disappearing, but a single
definitive cause has yet to be determined. Many potential causes have been
suggested. Some of the plausible theories include:
Historic honey bee diseases: These include American foulbrood,
European foulbrood, chalkbrood, Nosema, and approximately 15
known viruses. In some locations, strains of foulbrood have been become
resistant to the antibiotics traditionally used for their control. While
any of these pathogens are potential factors in honey bee decline, none
of them, alone or in known combination, produce the symptoms associated
with CCD.
Exotic or previously unknown bee diseases: World commerce and the
shipment of agricultural and apicultural stocks around the globe have
resulted in the introduction of numerous diseases and invasive pest
species in the past. It is highly probable that exotic species will
continue to enter the country accidently. Further investigation may
reveal the presence of a previously unknown pathogen present in CCD-affected bees.
Arthropod parasites of bees: These include the mites Varroa
desctructor and Acarapis woodii, both of which are
blood-feeders and are potential vectors of honey bee pathogens. They can
also be responsible for bacterial infections caused by breeching the
integument of the bee. The symptoms associated with the mites themselves
do not reflect those of CCD, but they can likely be responsible for
depressing general bee immune health, making the bees more susceptible
to other maladies.
Queen bee genetics: A relatively small number (in the hundreds)
of breeder queens are used in the U.S. to supply the millions of queen
bees produced. This lack of genetic diversity may have increased
susceptibly to imported or exotic pathogens. Additionally, feral
populations that once thrived in the wild through natural selection were
effectively eliminated by parasitic mites, and no longer contribute
substantial genetic variability to the managed bee populations.
Chemicals used in bee hives: While previously opposed to the use
of chemical pesticides around their bees, beekeepers have come to accept
and largely depend upon chemicals to combat parasitic mites and other
hive pests in order to maintain their colonies. Investigations have
found negative sub-lethal effects on honey bee health associated with
these chemicals, even when used in accordance with their labels. Many of
these chemicals accumulate in the beeswax combs, and long-term exposure
to them may be a key factor in the CCD mystery.
Chemicals in the environment: While foraging for food, honey bees
are exposed to numerous toxic substances. Investigations have shown that
residues and breakdown products from agricultural and household
pesticides, and from other sources of pollution, have been introduced to
the hive. Neonicotinoids, a relatively new class of chemical
insecticides, are highly toxic to bees, and can cause behavioral changes
to bees at sub-lethal doses. The non-target effects of these chemicals
could be considered as a potential factor in CCD.
Honey bee nutrition: Studies have indicated that honey bee larvae
develop best when fed a diet of pollen from diverse plant sources.
Forcing bees to forage in monocrop agriculture systems allows little
variety in their diets. Additionally, where herbicide-resistant crops
are grown, both the crop field and its borders are kept free of
flowering weeds, further reducing the nutritional value of the land for
bees and other beneficial insects. Feeding bees a winter diet of
high-fructose corn syrup by some beekeepers, followed by soy-based
pollen substitutes to initiate brood rearing early in the spring, has
been suggested to affect the overall health of the bees. However, the
methods of providing bees with winter food vary significantly among
beekeepers, and no clear correlation has been made to link this practice
with CCD.
Apicultural management practices: The ways in which bee colonies
are maintained (for honey production, pollination, queen or package bee
production, etc.) and how they are routinely handled varies considerably
among beekeepers, and cannot be clearly linked to CCD. However, poor
management practices, as in any system, can render a bad situation
worse.
Because no clear cause (either a single factor or a combination of factors)
for CCD has been established and demonstrated experimentally, a treatment for
CCD is not currently possible. Many potential causes are currently being
investigated. Members of the CCD Working Group, composed of academic,
commercial, and government scientists, initiated the first efforts to determine
the cause of CCD. Additional federal and state agencies, university researchers,
and private institutions have also begun to participate in various aspects of
these investigations. Different groups or researchers have focused on
determining specifically which, if any, of these above factors can be associated
with CCD, individually or in combination. Research efforts have generally
involved two components:
- Surveys and data collection: A number of surveys have been
initiated to determine the extent of CCD and associate the various
management practices and conditions under which bees are kept. But these
surveys have been too limited in scope or flawed in design to generate
accurate statistics. Additionally, the lack of dead bees in collapsed
colonies has made the diagnosis of pathogens difficult or impossible to
identify. Regular sampling of honey bees from apparently healthy
colonies, which are preserved for later diagnosis, may be useful for
evaluation if sudden declines are seen in these same populations.
- Analysis of sampling: Samples of honey bees, bee parasites and
hive products (wax, honey, propolis, and pollen) are currently being
analyzed by different groups for the presence of disease-causing
organisms, viruses, parasites, and chemical contaminates. Additionally,
molecular and genetic analysis of the bees and pathogens is being
conducted. Genetic markers for disease-resistance in honey bees are
being sought for use in breeding programs. Methods for rapidly
determining the presence of pathogens are also being developed. Factors
affecting honey bee health are also being quantified by measuring the
levels of stress-induced proteins.
Currently, little can be stated decisively on the causes of this phenomenon.
For now attempts to effectively prevent CCD can only be based on improving the
overall health of honey bees and their foraging habitat, and reducing known
sources of bee stress and mortality. Beekeepers should keep colonies strong by
using best-management practices that include common sense:
- Combining collapsing
colonies with healthy ones should be avoided;
- equipment from collapsed colonies
should not be re-used without adequate sterilization;
- IPM should be used to
reduce dependence on in-hive chemicals as well as reduce the levels of pesticide
exposure that bees contact while outside the hive
- breeding programs should be
pursued to produce hybrid bee stocks resistant to mite parasites and other
diseases;
- and research conducted to establish best-management practices should
be made available and disseminated easily through regional, state, and local
beekeeping networks.
For further reading, the CCD Working Group maintains a list of reports and
research updates online at:
http://maarec.cas.psu.edu/ColonyCollapseDisorderInfo.html
The CCD Action Plan (June 20, 2007) details some of the principle investigators
and areas of research associated with the current honey bee disappearances:
http://www.ars.usda.gov/is/br/ccd/ccd_actionplan.pdf
A map showing states affected by CCD (as of winter 2007) can be found at:
http://beealert.blackfoot.net/~beealert/USshaded.pdf
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