No end to controversy over cause of bee demise

By Sara Wyant

© Copyright Agri-Pulse Communications, Inc.

WASHINGTON, April 11, 2012 -Honeybee populations, which faced losses between 30% and 90% of honeybee colonies since 2006, continue to face steady declines while exact causes are yet to be found, said USDA Agricultural Research Service (ARS) research entomologist, Jay Evans.

Mickaël Henry published a study for Science last month that described colony collapse disorder (CCD) as “a recent, pervasive syndrome affecting honeybee colonies in the Northern hemisphere, which is characterized by a sudden disappearance of honeybees from the hive.

“Multiple causes of CCD have been proposed, such as pesticides, pathogens, parasites, and natural habitat degradation,” states the study. “However, the relative contribution of those stressors in CCD events remains unknown.”

While colony collapse disorder (CCD) now constitutes approximately 10% of hive failures, total colony die-offs remain at 30% each winter for the past five or six years, Evans said. A 2009 ARS survey indicated about 26% of those surveyed reported that some of their colonies died of CCD, while 36 percent said the same in 2007-2008 surveys.

 Together we can feed the Bees

Researchers are testing various pesticides, chemicals, pathogens and other factors to determine their effects on bees. Several studies recently identify agricultural, neonicotinoid pesticides as the cause of pollinator deaths and link certain pesticides specifically to CCD. According to a study from Harvard School of Public Health (HSPH), the likely culprit in worldwide declines in honeybee colonies since 2006 is imidacloprid, a widely used pesticide.

The authors, led by associate professor of environmental exposure biology in the Department of Environmental Health, Chensheng Lu, wrote that the research provides “convincing evidence” of the link between imidacloprid and CCD.

However, other outlets argue the study, which is set to appear in the June issue of the Bulletin of Insectology, calculated unrealistically high doses of the pesticide to reach its findings.

Lu and his co-authors hypothesized that the uptick in CCD resulted from the presence of imidacloprid, a neonicotinoid introduced in the early 1990s. Bees can be exposed in two ways: through nectar from plants or through high-fructose corn syrup beekeepers use to feed their bees.

Bayer CropScience described the scientists' claims as “spectacularly incorrect.”

“The study bees were fed HFCS spiked with different levels of imidacloprid that were far above real-world exposure levels,” states Bayer. The company also claims that “the authors ignored the scientific consensus that bee health is impaired by multiple factors, including inadequate diet, pests and parasites such as the varroa mite, microbial diseases, mismanaged colonies, and loss of genetic diversity.”

A separate study published in Science, by University of Stirling, UK, School of Natural Sciences researcher Penelope Whitehorn, said scientists there exposed colonies of a bee species in the lab to “field-realistic levels” of the neonicotinoid imidacloprid. According to the study results, treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared to control colonies.

“Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumble bee populations across the developed world,” states the Whitehorn study. 

However, CropLife America, the trade group representing crop protection firms, maintains that the Science studies do not accurately reflect natural field environments and that EPA tests do not reflect the same results regarding pesticides.

The EPA requires scientific pollinator toxicity studies as part of the data package necessary to register a pesticide, says CropLife. These tests must replicate outdoor use patterns when crops may be in bloom and attract bees.

“Only after rigorous review of these studies and others, will EPA approve a pesticide for use. It is crucial for pesticide applicators to follow instructions on the pesticide label, which may include options to reduce pesticide impact on bees,” the organization says. CropLife also says applicators may plan their application to avoid times when bees are present; not spray during flowering; and reduce exposures associated with pesticide-treated crop seeds.

“It takes more than labeling; it takes best management practices,” said Christi Heintx, executive director of Project Apis m., a coalition of beekeeper and orchadist groups formed to fund honeybee research. However, she told a CropLife conference earlier this month, that more data on the benefits of best management practices, like night spraying, is needed, as well as outreach efforts to growers.

She cited research that suggests more land dedicated to wildflowers, specifically the mustard plant, will benefit honeybees. Outreach efforts to encourage more beekeepers to plant those foraging crops and more growers to utilize fallow land for bee forage would serve to improve bee nutrition. She suggested an alternative to banning certain pesticides, which may be necessary to protect crops, could be to provide forage areas for bees.

“Neonicotinoids are critical for our pest control right now and alternatives are very limited,” said National Cotton Council integrated pest management manager Don Parker. “Cotton producers are not trying to have a negative impact on beekeepers. We're now running into a scenario where we have to have a much clearer understanding of the relationship between the cotton crop and bees.”

The EPA is currently evaluating neoniconitoids, but a petition circulating through with hundreds of thousands of signatures, asks the EPA to “act now to ban the sale of Bayer's neoniconitoid products.” The petition cites the studies published in Science as adding “substantial weight to the growing body of evidence showing that widespread use of nicotine-based insecticides called neonicotinoids is linked to Colony Collapse Disorder.”



Original story printed in April 11th, 2012 Agri-Pulse Newsletter.

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