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One of the more common general hypotheses concerns pesticides (or, more specifically, insecticides). It is particularly difficult to evaluate pesticide contributions to CCD for several reasons. First, the variety of pesticides makes it difficult to test all possible pesticides simultaneously. Second, many commercial beekeeping operations are mobile, transporting hives over large geographic distances over the course of a season, potentially exposing the colonies to different pesticides at each location. Third, the bees themselves place pollen and honey into long-term storage, effectively meaning that there may be a delay of anywhere from days to months before contaminated provisions are fed to the colony, negating any attempts to associate the appearance of symptoms with the actual time at which exposure to pesticides occurred.
One recently published view is that bees are falling victim to new varieties of nicotine-based pesticides; beekeepers in Canada are also losing their bees and are blaming neonicotinoid pesticides. To date, most of the evaluation of possible roles of pesticides in CCD have relied on the use of surveys submitted by beekeepers, but it seems likely that direct testing of samples from affected colonies will be needed, especially given the possible role of systemic insecticides such as the neonicotinoid imidacloprid (which are applied to the soil and taken up into the plant's tissues, including pollen and nectar).
The known effects of imidacloprid on insects, including honey bees, are consistent with the symptoms of CCD. For example, the effects of imidacloprid on termites include apparent failure of the immune system, and disorientation. In Europe the interaction of the phenomenon of "dying bees" with imidacloprid, has been discussed for quite some time now. It was a study from the "Comité Scientifique et Technique (CST)" which was in the center of discussion recently. In this research five other insecticides based on fipronil were also accused of killing bees.
Around the same time that French beekeepers succeeded in banning neonicotinoids, the Clinton administration permitted pesticides which were previously banned, including imidacloprid. In 2004, the Bush Administration reduced regulations further and pesticide applications increased. Some have claimed use of neonicotinoids on crops may be linked to the increase in cases of CCD in the United States since 2004, but there is no research yet to support such a connection.
In 2005, a team of scientists led by the National Institute of Beekeeping in Bologna, Italy, found that pollen obtained from seeds dressed with imidacloprid contains significant levels of the insecticide, and suggested that the polluted pollen might cause honey bee colony death. Analysis of maize and sunflower crops originating from seeds dressed with imidacloprid suggest that large amounts of the insecticide will be carried back to honey bee colonies. Sub-lethal doses of imidacloprid in sucrose solution have also been documented to affect homing and foraging activity of honeybees.
Imidacloprid in sucrose solution fed to bees in the laboratory impaired their communication for a few hours. Sub-lethal doses of imidacloprid in laboratory and field experiment decreased flight activity and olfactory discrimination, and olfactory learning performance was impaired. However, no detailed studies of toxicity or pesticide residue in remaining honey or pollen in CCD-affected colonies have been published so far, so, despite the similarity in symptoms, no connection of neonicotinoids to CCD has yet been confirmed.
Pesticides
One of the more common general hypotheses concerns pesticides (or, more specifically, insecticides). It is particularly difficult to evaluate pesticide contributions to CCD for several reasons. First, the variety of pesticides makes it difficult to test all possible pesticides simultaneously. Second, many commercial beekeeping operations are mobile, transporting hives over large geographic distances over the course of a season, potentially exposing the colonies to different pesticides at each location. Third, the bees themselves place pollen and honey into long-term storage, effectively meaning that there may be a delay of anywhere from days to months before contaminated provisions are fed to the colony, negating any attempts to associate the appearance of symptoms with the actual time at which exposure to pesticides occurred.
One recently published view is that bees are falling victim to new varieties of nicotine-based pesticides; beekeepers in Canada are also losing their bees and are blaming neonicotinoid pesticides. To date, most of the evaluation of possible roles of pesticides in CCD have relied on the use of surveys submitted by beekeepers, but it seems likely that direct testing of samples from affected colonies will be needed, especially given the possible role of systemic insecticides such as the neonicotinoid imidacloprid (which are applied to the soil and taken up into the plant's tissues, including pollen and nectar).
The known effects of imidacloprid on insects, including honey bees, are consistent with the symptoms of CCD. For example, the effects of imidacloprid on termites include apparent failure of the immune system, and disorientation. In Europe the interaction of the phenomenon of "dying bees" with imidacloprid, has been discussed for quite some time now. It was a study from the "Comité Scientifique et Technique (CST)" which was in the center of discussion recently. In this research five other insecticides based on fipronil were also accused of killing bees.
Around the same time that French beekeepers succeeded in banning neonicotinoids, the Clinton administration permitted pesticides which were previously banned, including imidacloprid. In 2004, the Bush Administration reduced regulations further and pesticide applications increased. Some have claimed use of neonicotinoids on crops may be linked to the increase in cases of CCD in the United States since 2004, but there is no research yet to support such a connection.
In 2005, a team of scientists led by the National Institute of Beekeeping in Bologna, Italy, found that pollen obtained from seeds dressed with imidacloprid contains significant levels of the insecticide, and suggested that the polluted pollen might cause honey bee colony death. Analysis of maize and sunflower crops originating from seeds dressed with imidacloprid suggest that large amounts of the insecticide will be carried back to honey bee colonies. Sub-lethal doses of imidacloprid in sucrose solution have also been documented to affect homing and foraging activity of honeybees.
Imidacloprid in sucrose solution fed to bees in the laboratory impaired their communication for a few hours. Sub-lethal doses of imidacloprid in laboratory and field experiment decreased flight activity and olfactory discrimination, and olfactory learning performance was impaired. However, no detailed studies of toxicity or pesticide residue in remaining honey or pollen in CCD-affected colonies have been published so far, so, despite the similarity in symptoms, no connection of neonicotinoids to CCD has yet been confirmed.
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