Post by Christina Locke and Claudio Gratton
We are often asked about neonicotinoid pesticides, or “neonics”, and their effects on bees. Neonics are the most widely used insecticides globally, and are in the news a lot these days due to concerns about their effects on birds, fish and beneficial insects including pollinators. Some countries, states and municipalities have moved to limit their use because of these concerns.
Neonics became commercially available in the 1990s and quickly became popular for their high toxicity to insects and relatively low toxicity to vertebrates. Neonics are water soluble, systemic insecticides, which means they can be taken up by a plant’s roots and spread to the whole plant, including its pollen and nectar. Unlike other classes of pesticides like pyrethroids that are acutely toxic to insects but break down quickly in the environment, neonics persist in plants, soil and water for long periods of time–weeks to months, and even longer in soil and woody vegetation. Besides concerns about acute toxicity of adult bees, there are serious concerns of chronic sub-lethal effects (like confusion) that affect bee behavior and colony health over time. Many laboratory studies have shown detrimental effects of neonics on bee feeding, learning and memory. Four of the five most common neonics are considered highly toxic to bees when bees are exposed directly to the chemical or its residues. However, field studies have been less conclusive and most show little effect of neonics on honeybees. This doesn’t mean that neonics are off the hook. A well designed study recently published in Nature shows significant adverse effects of neonic seed treatments on wild bees. Bumblebee colony growth and reproduction, as well as solitary bee nesting, were reduced in fields treated with neonics while effects on honeybees were not detected. Exposure to neonics is especially of concern in mass-flowering crops like canola that are very attractive to pollinators. In cities, too, inappropriate neonic use on highly attractive flowering trees can lead to massive bee kills.
U.S. EPA action on neonics
The U.S. Environmental Protection Agency (EPA) has taken several steps in the past several years regarding neonics and honeybee testing:
Change in pesticide risk assessment protocol to a tiered system that tests pesticide effects on multiple honeybee life stages and colony-level effects. Old testing methods focused only on adult bees.
Review of neonicotinoids began in 2008 and is scheduled for completion in 2016 for most neonics.
No new registered uses will be allowed for neonics until new risk assessments are complete.
New labeling requirements for pesticides known to be toxic to honeybees (see photo at right).
Proposed prohibition of neonic use on flowering crops where contracted pollinators (usually managed honeybees) are present. This restriction is currently undergoing public review through June 29–go to regulations.gov to submit a comment on docket “Mitigation for Pesticide Products that are Acutely Toxic to Bees.”
Investigating bee kills tied to specific pesticides through a voluntary bee kill reporting system (anyone can report a bee kill).
Guidelines to assist states and tribes developing their own pollinator protection plans. Federal funding may also become available to support plan development.
Of course, there are limitations of these actions. The EPA pesticide risk assessments test effects on honeybees only, not other pollinators like wild bees and butterflies, and not insects that eat crop pests like lady beetles. Though neonics are more toxic to insects than other organisms, they can and do affect vertebrates. In birds, direct ingestion of neonic-treated seed is associated with decreased egg size, lower fertilization rates and death. There is room to expand the dialogue on neonic seed treatments, the use of which is widespread, and at least in soybeans has no clear yield benefit. Even as movements are taken on neonics, new systemic pesticides like flupyradifurone are being approved, and although they are purported to be less detrimental to bees than neonics, they have not yet undergone as much scientific scrutiny. Still, protections designed for honeybees are expected to benefit other beneficial insects, and steps taken thus far by EPA can be considered steps in the right direction for pollinator protection.
It’s more than just pesticides
Bee declines are the ultimate effect of many combined insults, and a multi-faceted approach is necessary to ensure pollinator health into the future. Honeybees and wild bees are both affected by habitat loss, and may face nutritional deficiencies when areas of highly diverse flowering plants, like prairies, are replaced by large crop fields where only one type of plant blooms at a time. Furthermore, social bees are hit by a variety of colony pests and pathogens that compromise their immune systems. Diseases, parasites, pesticides, habitat loss, and poor nutrition act together to hit pollinator communities hard. The newly released White House Strategy outlines national efforts to increase pollinator habitat, address beekeeping concerns, and reconsider the widespread use of neonics. Though some will argue that these measures do not go far enough towards pollinator conservation, it is truly remarkable to see pollinator issues on the national agenda and part of everyday dialogues in agency settings and public arenas.This article was posted in Lab Blog, Policy, Pollinators and tagged bees, neonicotinoids, pesticides, pollinators.