25 July 2013 19:35 [Source: ICIS news]
WASHINGTON (ICIS)--Fungicides have become a new focus in the investigation into the wide scale losses among US bee colonies, the US Department of Agriculture (USDA) said in a report circulated on Thursday.
The level of fungicides in the collected pollen samples was too low to cause a bee’s death, the study said, “but it still may leave them more susceptible to infection by a gut parasite”.
Although traces of multiple insecticides, herbicides, miticides and fungicides were found in pollen collected by bees, said the study, “fungicides were the most frequently found chemical substance in the pollen samples”.
“The most common was the fungicide chlorothalonil, which is widely used on apples and other crops,” ARS researchers said.
US agricultural research scientists have struggled for years to find the cause of the worrying colony collapse disorder (CCD).
CCD is an epidemic characterised by a sudden disappearance of a colony’s bees with few, if any, dead bees left behind. For reasons unknown, a colony’s bees will fly off and never return.
Although the disorder may have been building for several years, it first came to crisis-level attention after the 2006-2007 North American winter season, when 32% of the nation’s cultivated bee colonies disappeared.
Since its onset in 2006-2007, colony collapse disorder has been blamed for an annual loss of about 30% of the ?xml:namespace>
That rate of year-by-year loss is not sustainable, according to ARS, and the continuing impact of the disorder puts a major part of US agriculture at risk.
ARS officials say that about one-third of the
In a comprehensive study issued in May this year, the USDA and the Environmental Protection Agency (EPA) found that CCD involved many potential factors, including parasites and disease, genetics, poor nutrition and possibly pesticide exposure.
In the most recent study, ARS researchers used the bee-gathered pollen that contained trace elements of fungicides to feed a fresh bee colony.
“Honey bees that were fed pollen that contained the fungicide chlorothalonil and was collected at the hive entrance were almost three times more likely to become infected when exposed to the parasite Nosema, compared with control bees,” said ARS researcher Jeff Pettis.
“Our study highlights the need to closely look at fungicides and bee safety,” said study co-author Dennis vanEnglesdorp, “as fungicides currently are considered safe and can be sprayed during the bloom on many crops.”
The new ARS study appears to shift the focus from pesticides - which cannot be applied to crops when pollination is under way - to fungicides, at least as a potential contributing factor.
The new report comes as legislation has been introduced in the US House that would require EPA to suspend the use of certain approved insecticides, a group called neonicotinoids, and bar new approvals until scientific evidence and field studies can prove they do not cause harm to pollinators.
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