Abstract

The European honeybee, Apis mellifera, is an important pollinator of agricultural crops. Since 2006, when unexpectedly high colony losses were first reported, articles have proliferated in the popular press suggesting a range of possible causes and raising alarm over the general decline of bees. Suggested causes include pesticides, genetically modified crops, habitat fragmentation, and introduced diseases and parasites. Scientists have concluded that multiple factors in various combinations—including mites, fungi, viruses, and pesticides, as well as other factors such as reduction in forage, poor nutrition, and queen failure—are the most probable cause of elevated colony loss rates. Investigators and regulators continue to focus on the possible role that insecticides, particularly the neonicotinoids, may play in honeybee health. Neonicotinoid insecticides are insect neurotoxicants with desirable features such as broad-spectrum activity, low application rates, low mammalian toxicity, upward systemic movement in plants, and versatile application methods. Their distribution throughout the plant, including pollen, nectar, and guttation fluids, poses particular concern for exposure to pollinators. The authors describe how neonicotinoids interact with the nervous system of honeybees and affect individual honeybees in laboratory situations. Because honeybees are social insects, colony effects in semifield and field studies are discussed. The authors conclude with a review of current and proposed guidance in the United States and Europe for assessing the risks of pesticides to honeybees.

Highlights

  • The European honey bee, Apis mellifera, plays an important role as a pollinator for major agricultural crops, pollinating $15 billion to $20 billion worth of crops in the United States alone and more than $200 billion worldwide [1]

  • While it is undeniable that overwintering losses of commercial honeybee colonies are higher than they were in the recent past, there is no clear indication that pesticides are the root cause of such losses

  • The US Department of Agriculture (USDA) survey shed light on the pattern of honeybee losses across the United States and concluded that such losses were unrelated to the patterns of agricultural pesticide use, in general, or neonicotinoid use, in particular

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Summary

Risks of Neonicotinoid Insecticides to Honeybees

Anne Fairbrother,*y John Purdy,z Troy Anderson,x and Richard Fellk yExponent, Bellevue, Washington zAbacus Consulting Services, Campbellville, Ontario, Canada xDepartment of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, USA kDepartment of Entomology, Virginia Tech, Blacksburg, Virginia, USA. Neonicotinoid insecticides are insect neurotoxicants with desirable features such as broad-spectrum activity, low application rates, low mammalian toxicity, upward systemic movement in plants, and versatile application methods. Their distribution throughout the plant, including pollen, nectar, and guttation fluids, poses particular concern for exposure to pollinators. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc., on behalf of SEATC.

Introduction
Honey Bee Life Cycle
Possible Causes of Colony Loss
Neonicotinoid Insecticides
Neonicotinoid chemistry and modes of action
Effects of neonicotinoid exposure on honeybees
Risk Assessment Frameworks
Brood Colony strengths
Risk characterization
Findings
Conclusions and Summary
Full Text
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