What are neonicotinoids used for?

As massive numbers of bees and other pollinators keep dying across the globe, study after study continues to connect these deaths to neonicotinoid pesticides (A.K.A. “neonics”). With the science piling up, and other countries starting to take critical pollinator-saving action, here’s a quick primer on all things neonics:

What are neonics?

A: Neonics are neurotoxic insecticides, meaning they are pesticides designed to kill insects by attacking their nerve cells. Neonics permanently bind to nerve cells, overstimulating and destroying them. Insects poisoned with neonics often exhibit uncontrollable shaking or twitching, paralysis, and—eventually—death.

A bee.

Neonics are also “systemic,” meaning they dissolve in water and are absorbed by plants, making the plant itself—including its nectar, pollen, and fruit—toxic. Neonics are often applied as a “drench” to a plant’s roots, or as a coating on a plant’s seed, which the plant then soaks up as it grows. The levels applied can often be so high that they make the plant toxic to insects for years after the initial treatment.

Where are neonics used?

A: Everywhere. Neonics are the most popular insecticides in the U.S. and can be found in lawn and garden bug sprays, flea and tick treatments for pets and livestock, and food grown in farm fields across the country. As this map* shows, the neonic imidacloprid is used just about every place that people grow crops. And that’s just the tip of the iceberg—the map doesn’t account for non-agricultural uses (e.g., golf courses, lawns, gardens) or the four other neonic chemicals also extensively used in the U.S.

Do neonics harm bees?

A: Absolutely. Neonics are designed to kill insects, and bees are insects. A large and growing body of research shows that neonic use is a leading cause of the massive bee die-offs around the globe that threaten our food security, agricultural economy, and environment. Bees at risk include not only commercial honey bees, but the more than 4,000 species of native bees that live in the U.S., like the rusty patched bumble bee or the bees seen here in every color of the rainbow.

A wild blue bee in the wild. Photo by Bob Peterson.

Do neonics harm other wildlife?

A: Yes. Neonic use has been shown to cause significant losses of aquatic invertebrates, a critical food source to birds and fish. Neonic use has also been linked with documented losses of bird and butterfly populations.

Do neonics contaminate our water?

A: Yes. Neonics can persist in soil for a long time, where rain or irrigation water easily carries them into surrounding lakes, streams, or sources of drinking water. The U.S. Geological Survey (USGS) has found that neonics contaminate waterbodies nationwide, often at levels that harm critical aquatic insects and other wildlife. That’s no surprise given how wastefully neonics are often applied. For example, when neonics are applied as seed treatment, only about 5% of the pesticide is absorbed by the plant at best—the other ~95% stays in the soil. And with up to 100% of conventional corn and 50% of soybean seed now treated with neonics, it’s not hard to guess how they keep ending up in our water.

Are neonics in our food?

A: Yes. Neonic residues are found in 86% of honey in the U.S. and also in apples, cherries, strawberries, baby food, and other foods popular with kids and adults alike. Because neonics are actually inside the fruit, vegetables, and other foods we eat, they can’t be washed off.

Is there concern that neonics may be harming our health?

A: Yes. Neonics attack parts of insect nerve cells that are similar to those found in humans, making researchers and health experts concerned that what’s bad for bees could be bad for us too. In particular, emerging research suggests that exposure to neonics in the womb or early in life could be linked with developmental defects, heart deformations, muscle tremors, and memory loss.

A dead bee.

What is our federal government doing about neonics?

A: Not much. Several years back, the U.S. EPA introduced the “bee hazard” icon and limited restrictions for some neonic products, but these baby steps have failed to stem massive bee and pollinator losses. EPA has also long been studying the impacts of neonics through its “registration review” process. Although these reviews could result in life-saving protections for pollinators, don’t hold your breath—EPA just quietly pushed back the deadlines for their completion, and isn’t expected to take needed action anyway while still under Trump and Andrew Wheeler’s direction.

What have other countries done?

A: Other countries are moving to ban outdoor uses of neonics. In 2018, The European Union voted to completely ban all outdoor uses of three neonics, citing their impacts to honey bees. Canada recently followed suit, recommending that the country similarly phase out all outdoor uses of the same neonics in 3-5 years.

What should replace neonics if we limited their use?

A: For the most part, nothing. Neonics are often used where they simply aren’t effective. In 2014, EPA found that neonic soybean seed treatments “likely provide $0 in benefits to growers,” yet up to half of all conventional soybean seed is still neonic-treated. Other recent research shows neonics to be similarly ineffective on corn, yet up to 100% of conventional corn seed gets a neonic treatment. These uses account for the vast bulk of neonics entering the environment and—since they don’t work—they don’t need replacing. Agroecological practices—like diverse crop rotations, cover cropping, and introducing natural enemies of crop pests (AKA “good bugs”)—can eliminate the need for other neonic uses. In those instances where an insecticide is needed, less harmful substitutes for neonics are available.

*This map is from 2014, the last year USGS included neonic-treated seeds in its annual pesticide survey (even though treated seed usage has not diminished since). To understand how massive treated seed use is, compare this map to the 2015 map, and see the world of difference for yourself.

About the Authors

Staff Attorney, Pollinator Initiative, Wildlife Division, Nature Program

Neonicotinoids

Some facts about neonicotinoids

  • Neonicotinoids are active substances used in plant protection products to control harmful insects, which means they are insecticides
  • The name literally means “new nicotine-like insecticides”. They are chemically similar to nicotine
  • The name neonicotinoids is sometimes shortened to “neonics” or “NNIs”
  • The first neonic was approved in the EU in 2005
  • Neonics are systemic pesticides. Unlike contact pesticides, which remain on the surface of the treated parts of plants (e.g. leaves), systemic pesticides are taken up by the plant and transported throughout the plant (leaves, flowers, roots and stems, as well as pollen and nectar)
  • Neonics are much more toxic to invertebrates, like insects, than they are to mammals, birds and other higher organisms
  • Neonics affect the central nervous system of insects, leading to eventual paralysis and death
  • They are also common in veterinary applications such as tick control and flea collars for pets

Current status of the neonicotinoids in the EU

In 2013, five neonicotinoid insecticides were approved as active substances in the EU for the use in plant protection products, namely clothianidin, imidacloprid, thiamethoxam, acetamiprid and thiacloprid.

The Commission closely monitors the possible relations between bee health and pesticides and is determined to take the most cautious approach possible to protect bees.

In 2013, the Commission severely restricted the use of plant protection products and treated seeds containing three of these neonicotinoids (clothianidin, imidacloprid and thiamethoxam) to protect honeybees (see Regulation (EU) No 485/2013).

The measure was based on a risk assessment of the European Food Safety Authority (EFSA) in 2012. It prohibits the use of these three neonicotinoids in bee-attractive crops (including maize, oilseed rape and sunflower) with the exception of uses in greenhouses, of treatment of some crops after flowering and of winter cereals. At the same time, the applicants of the three substances were obliged to provide further data (so-called “confirmatory information”) for each of their substances in order to confirm the safety of the uses still allowed.

Following the assessment of this confirmatory information by EFSA of clothianidin, imidacloprid and thiamethoxam, the remaining outdoor uses could no longer be considered safe due to the identified risks to bees. Therefore, the Commission services prepared in 2017 three proposals to completely ban the outdoor uses of the three active substances.

EFSA has evaluated data collected in an open call for the review of the 2013 restrictions for the above-mentioned neonicotinoids as foreseen in Regulation (EU) No 485/2013. The deadline for this evaluation was postponed to February 2018 due to the amount of data to be assessed, the complexity of the request and to give Member States experts sufficient opportunity to comment on EFSA’s draft conclusions. The EFSA Conclusions on the risk assessment for the active substances clothianidin, imidacloprid and thiamethoxam were published on the EFSA website on 28 February 2018. The Commission and the Member States have examined these conclusions thoroughly and concluded that they confirm the already identified risks for outdoor uses.

Therefore, the Commission services maintained the proposals to completely ban the outdoor uses of the three active substances and these were supported by a qualified majority of Member States in the Regulatory Committee on 27 April 2018. The Commission Implementing Regulations amending the conditions of approval of the active substances imidacloprid, clothianidin and thiamethoxam have been published in the Official Journal of the European Union on 30 May 2018. As a result, all outdoor uses of the three substances are banned and only the use in permanent greenhouses remains possible.

  • Regulation restricting the use of imidacloprid
  • Regulation restricting the use of clothianidin
  • Regulation restricting the use of thiamethoxam

In the light of these restrictions, the applicants for the renewal of approval of clothianidin and thiamethoxam withdrew their applications. Consequently, the approval of these substances expired on 31 January 2019 and 30 April 2019, respectively. The deadline for submission of the renewal dossier for imidacloprid is 31 January 2020. The expiry date for imidacloprid is 31 July 2022.

For another neonicotinoid, acetamiprid, EFSA established a low risk to bees. A ban or further restrictions of this substance is therefore neither scientifically nor legally appropriate. A draft Regulation proposing a renewal of approval has been presented to the Member States on 5-6 October 2017. The proposal was further discussed and presented to the Member States for opinion in the Regulatory Committee on 12 and 13 December 2017. The Committee gave a favourable opinion on the draft Regulation with a qualified majority of Member States. The Regulation renewing the approval until 28 February 2033 has been published in the Official Journal of the European Union.

A fifth neonicotinoid, thiacloprid is a candidate for substitution, based on its endocrine disrupting properties. Candidates for substitution are pesticides for which national authorities need to carry out an assessment to establish whether more favorable alternatives to using the plant protection product exist, including non-chemical methods. The approval for thiacloprid expires on 30 April 2020. Based on the EFSA conclusion which was published at the beginning of 2019, the Commission had proposed to the Member States in the Regulatory Committee not to renew the approval. On 22 October, the Committee gave to this proposal a favourable opinion on the draft Regulation, with a qualified majority of Member States. The Commission adopted the Regulation on 13 January 2020.

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Neonicotinoid insecticides are widely used in agricultural and urban settings. Released in the mid-1990s as an alternative to older organophosphate and carbamate insecticides, neonicotinoid insecticides are highly toxic to many invertebrates, including bees. They are systemic, meaning they are absorbed and retained in plant tissues, making all parts of the plant toxic to insects. Even very small concentrations of these insecticides found in the pollen and nectar of treated plants can be harmful to pollinators (for a review of recent research, see the Xerces Society report, How Neonicotinoids Can Kill Bees)

What’s more, most neonicotinoids are highly persistent, sometimes remaining at harmful levels in woody plants and soil for months to years after they were applied (Jones et al. 2014). Untreated plants sown in areas formerly treated with neonicotinoids, such as cover crops that follow a rotation of treated corn or soybeans, can pick up residues from these prior applications (Bonmatin et al. 2005). In addition, neonicotinoids applied to crops can contaminate plants in surrounding areas, which poses risk to the bees that visit these plants for pollen and nectar (Botías et al. 2015; Mogren and Lundgren 2016).

Different neonicotinoid insecticides have slightly different chemical structures, some of which are more toxic to bees. The “nitroguanidine” neonicotinoids (including imidacloprid, dinotefuran, clothianidin, and thiamethoxam) are a subgroup of neonicotinoids that contain a nitro functional group (-NO2) instead of a cyano functional group (-C=N) in their molecular structure. This slight difference in their molecular structure affects how these two subgroups of neonicotinoids bind to an insect’s receptor site. The nitro-group neonicotinoids are much more toxic to bees than the cyano-group neonics, which include acetamiprid and thiacloprid (Blacquière et al. 2012).

Jointly, the toxicity, systemic nature, and persistence of neonicotinoid insecticides pose a high risk to bees. For this reason, Bee Better prohibits any use of nitroguanidine neonicotinoids, the highly bee-toxic subgroup of neonicotinoids (e.g. imidacloprid, dinotefuran, clothianidin, and thiamethoxam).

Bee Better aims to establish and maintain healthy flowering habitat that can support bees and other beneficial insects. The persistence of neonicotinoids in soil can pose a contamination risk months to years after these chemicals are applied. Therefore, Bee Better pollinator habitat cannot be placed in areas where neonics were applied, including the planting of treated seed, in the previous two years. In addition, permanent pollinator habitat on Bee Better farms must be placed at least 125 feet away from areas currently treated – or suspected to be treated, in the case of neighboring land – with neonicotinoids.

Summary of Relevant Bee Better standards

Crops:
Do not use nitroguanidine neonicotinoids (clothianidin, dinotefuran, imidacloprid, and thiamethoxam). This ban includes the planting of treated seeds. (Standard 2.2e).

Habitat:
Do not plant pollinator habitat in locations where nitroguanidine neonicotinoids were applied in the previous two years. In the Bee Better certification process, use includes the planting of seeds treated with nitroguanidine neonicotinoids. (Standard 1.1a, vii).

Establish a pesticide-free buffer around permanent pollinator habitat. Spatial buffers should meet the following minimum width: 125 feet for seed treated with nitroguanidine neonicotinoids. (Standard 2.3c, i).

Buffers are required within your own property, as well as between new permanent pollinator habitat on your property and neighboring farms or land where insecticides are known or suspected to be applied. When insecticide application practices on neighboring properties change following permanent habitat creation on your parcels, spatial buffer requirements can be waived, although when feasible, we recommend incorporating a buffer. When permanent habitat is adjacent to farms containing canola, corn, cotton, soy, sunflower, and wheat, seed treatment buffers must be adhered to unless there is proof that neighboring farms are not treated with nitroguanidine neonicotinoids (e.g., they are certified organic). (Standard 2.3c, iii).

For more information on neonicotinoid risks to bees, see the following resources:

University of California IPM Bee Precaution Pesticide Rating. http://www2.ipm.ucanr.edu/beeprecaution/

Impact of Pesticides on Invertebrates database. https://pesticideimpacts.org/

What are Neonicotinoids?

Neonics affect the central nervous system of insects. They bind to receptors of the enzyme nicotinic acetylcholine, causing excitation of the nerves, leading to eventual paralysis and death. This specific neural pathway is more abundant in insects than warm-blooded animals, so these insecticides are selectively more toxic to insects than mammals.

Bees have a particular genetic vulnerability to neonics because they have more of these receptors than other insects, as well as more learning and memory genes for their highly evolved system of social communication and organisation, Unlike many insect pest species which are able to detoxify harmful chemicals, bees possess fewer genes for detoxification.

While the older organophosphate and carbamate insecticides tend to degrade quite rapidly in the environment, neonics are more persistent. Imidacloprid can last for months or years in soil and may leach into groundwater under some conditions.

Because they are biologically active at very low concentrations, neonics can be applied at much lower volumes in the field than the older groups of insecticides – in doses of a few grams, rather than kilos, per hectare of the active ingredient.

Neonics were originally welcomed as much safer for humans, livestock and birds than other insecticides. Seed treatments were seen as a more effective method of targeting pests than spraying crop foliage, and more environmentally-friendly because they can reduce the number of spray applications needed in-field. However, over time, it has become clear that they pose different and poorly understood risks to bees and other non-target invertebrates precisely because of the properties that have made them so useful to farmers: their systemic action; their persistence in crops and soil; and their potency at low concentrations. Added to this, their widespread use in many cropping systems and their unplanned presence in pollen and nectar builds up a worrying picture of low level but continued exposure for pollinators, which our regulatory risk assessment schemes are only starting to address.

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Last month the European Food Safety Authority (EFSA) concluded that certain neonicotinoids used on farms and gardens can harm honeybees, bumblebees and solitary bees. So why are the controversial insecticides still popular, how do they work and why they are of concern?

What are neonicotinoids?

First applied commercially in the 1990s, ‘neonics’ are among the most popular insecticides in the world. They are coated onto crop seeds and – being water soluble –taken up and dispersed throughout the plant. Sometimes they are sprayed onto foliage. They are especially effective against sucking pests (such as aphids), but also chewing insects.

Why are they so widely used?

Treating seeds with neonics can protect seedlings for up to 10 weeks, a vulnerable stage in their lives. This also reduces the need for multiple pesticide sprays. When neonics were introduced, carbamates, organochlorine and organophosphorus compounds dominated the market: these were not very selective and toxic to mammals. The newcomers were viewed as safer and more efficient.

So how exactly do they work?

Like nicotine, neonics work by binding to nerve cell receptors that usually respond to the neurotransmitter acetylcholine. At high doses, neonics over-excite neurons, which can lead to epileptic-like effects, cell death or nerve cell inactivation. At lower levels, normal neuronal function is impaired. It is suspected that this is how bees are harmed. After repeat exposure, target nerve cells become more vulnerable and toxicity to insects increases.

What did the EFSA review find?

The review looked at imidacloprid, clothianidin and thiamethoxam. The three pesticides were found to impact bee learning and navigation and reproduction, though the risk varies with route of exposure and between bee species. The technical reports update initial conclusions drawn up in 2013.

I thought the pesticides only target pests?

They do. However, nanogram quantities of the neurotoxin are present in pollen and nectar and these pose sub-lethal risks to pollinators, such as bees. Nearby crop and wild plants can also be contaminated and the insecticides can accumulate in soil. Neonics have been detected in streams, honey, garden flowers and wildflowers. It’s not just bees, either. A Dutch study reported that birds raised fewer chicks when levels of imidacloprid were higher in surface waters. The more present, the poorer the fare of aquatic invertebrates. A review last year highlighted potential links to butterfly declines and harm to ants, earthworms, mayflies and caddisflies.

Did regulators act to ban or restrict them?

There were restrictions put in place for three neonics since 2013 in their use in flowering crops, such as oil seed rape. However, the EFSA do not make specific legislative recommendations. Any moves in this direction are up to EU member states and the European Commission.

They are still used by farmers?

Yes. On wheat and barley, for instance, to limit the spread of a virus and deter slugs from hollowing out grain. Farmers say they are important for controlling aphids on sugar beet to limit spread of the beet yellow virus. Some neonics are used on fruiting trees in Europe.

What do opponents of neonicotinoids say?

That neonicotinoids are just one of a long line of pesticides that harm pollinators and non-target animals. One of the main arguments is that each insecticide’s effects are studied in isolation, but in the real world they occur as mixtures that may act synergistically and accentuate the risks to beneficial insects and other organisms. This, they suggest, means the approval system for new agrichemicals is faulty.

What does the agrichemical industry say about banning these pesticides?

That it will get more difficult to produce high quality food crops such as wheat, barley, vegetables and sugar beet at a competitive price. Also, that a ban could reduce competitiveness of European farmers and boost imports of wheat and sugar beet from countries that still use the neonics. Bayer (which sells imidacloprid and clothianidin) disputes the EFSA findings.

The main argument of those in favour of neonics is that environmental problems must be balanced against farm needs and that some neonics are far less toxic to bees than the three EFSA focus on. Rothamsted Research in the UK has previously argued that a neonic ban could harm UK agriculture.

There are three listed neonicotionids, but there are others out there?

The report focusses on the three most widely-used neonicotinoids, but others such as thiacloprid and acetamiprid are not subject to the moratorium or recent review. Some researchers say other newer insecticides may prove harmful to bees and other non-target insects because regulatory procedures have not changed. One example is sulfoxaflor, which works in a similar way to neonics and has been challenged in US courts

Will banning these neonicotinoids turn the situation around for our wild bees?

Not on its own. Scientists campaigning for a ban say bees face a wide range of other stresses, especially loss of habitat and the presence of other toxins in the environment, and the blame for loss of bees cannot be pinned entirely on one class of insecticide.

Neonicotinoid Pesticides

Neonicotinoids (also referred to as “neonics”) are insecticides derived from nicotine. They act by binding strongly to nicotinic acetylcholine receptors in the central nervous system of insects, causing overstimulation of their nerve cells, paralysis and death. Neonicotinoids are highly water soluble, persistent in the environment, and can migrate into all parts of treated plants.

Although their principal use is in agriculture for seed and soil treatment and on plant foliage, neonics may be used in home yards and gardens, golf courses, and for flea and tick treatments on dogs and cats. Introduced in Canada in the 1990s, five neonicotinoids are approved for agricultural use in Canada. Of these, acetamiprid and thiacloprid are permitted for limited purposes. In April 2019, the Pest Management Regulatory Agency (PMRA) of Canada released its re-evaluation of the three most widely used neonicotinoid substances: imidacloprid, clothianidin, thiamethoxam.

New regulations aimed at reducing the chance of pollinators coming into contact with plants and flowers contaminated by the three compounds will be phased in by the spring of 2021. Some regulatory changes include:

  • Most foliar applications prior to bloom will be disallowed;
  • Use on stone fruit, strawberries and some tree nuts will be discontinued;
  • New restrictions related to a number of other crops and soils have been introduced;
  • Additional precautions will now be required during the planting of neonicotinoid-treated seeds to avoid exposing pollinators to contaminated dust.

Further decisions aimed at protecting aquatic life are expected in early 2020 (Health Canada, 2017).

Public awareness of the hazards of neonicotinoids is from publicized concerns about deaths and colony collapse disorder among bees and other pollinator insects. As the overview below shows, there is evidence of environmental and dietary exposures to neonicotinoids and their metabolites among people, but also uncertainty regarding human health risks.

Tracing the environmental fate shows that neonicotinoids are found in environments and foods and on household pets:

  • Neonicotinoid residues have been detected in wetlands, surface water and agricultural soil in several Canadian studies (e.g., Schaafsma et al., 2015, Main et al., 2014).
  • Neonicotinoid residues are present in most edible parts of fruits and vegetables and cannot be washed off. Imidacloprid may have the highest detection rate (Chen et al., 2014).
  • Neonicotinoid residues from flea treatments on pets may be transferred for up to four weeks after application, potentially exposing people in contact with treated animals (Craig et al., 2005).

There is evidence that the general population is exposed to neonicotinoid pesticides through their diets. While average intakes of individual compounds associated with food consumption appear to be within safe levels, it is possible that certain segments of the population may have exposures above recommended levels:

  • Exposure estimates for the US population indicated that the although average dietary intake could be considered safe, potential for exposure above the chronic reference dose existed for people consuming large amounts of more heavily contaminated food items (e.g., squash and spinach) (Chang et al. 2018).
  • According to Health Canada, environmental amounts of neonicotinoids found in the environment are below levels of concern for human health (Health Canada, 2016). People handling neonicotinoid pesticides may have higher exposure risks than the general population but can minimize their risk by following safety precautions specified in the product labels (e.g., use of protective clothing and equipment) (Health Canada 2018).
  • A Japanese study found widespread exposures to neonicotinoid residues but intake levels of individual compounds were considered safe (Harada et al., 2016).

There are several human observational and animal studies indicating that there may be adverse developmental and neurological impacts from chronic exposure to neonicotinoid pesticides.

  • A systematic review of four general population studies suggested a link between chronic neonicotinoid exposure (all ages, including pre-natal) and adverse developmental or neurological outcomes (Cimino et al., 2017).
  • The European Food Safety Authority concluded that idiacloprid and ametamiprid may affect neuronal development and function, but further scientific study is warranted (European Food Safety Authority, 2014).

This topic page is intended to provide updated resources on the human health risks associated with neonicotinoid exposure, safer alternatives and knowledge gaps. In light of recent changes to regulations for this group of pesticides, the list also includes several evidence-informed documents prepared by regulatory authorities detailing new restrictions and guidelines and the rationale behind them. These documents also incorporate updated scientific evidence.

Selected External References

  • Neonicotinoids (European Commission, 2019)
    This document provides facts on neonicotinoids and information about actions taken by the European Commission to protect honeybees, including restrictions of 3 neonicotinoids commonly used in plant protection products and treated seeds. The report confirms that most neonicotinoids are more toxic to insects and other invertebrates than to humans and higher organisms; however, one compound, thiacloprid has endocrine disrupting properties and may not be re-approved in 2020.
  • Neonicotinoids: risks to bees confirmed (European Food Safety Authority, 2018)
    This document summarizes risk assessments and guidelines related to individual nicotinoids and the risks posed to pollinators. Links to the peer review of assessments are provided.
  • Update on the neonicotinoid pesticides (Health Canada, 2017)
    This document offers some background on use of neonicotinoids and concerns related to their effects on pollinators. A human health risk assessment for imidacloprid concluded that human health risks were within acceptable limits.
  • Case study: Neonicotinoids (Public Health Ontario, 2015)
    This case study describes the risks to bees from neonicotinoids, and provides information on regulation, ecosystem considerations and on food security, with consideration of residual concentrations of neonicotinoids in fruits and vegetables.

Peer-reviewed Publications

  • Alternatives to neonicotinoids (Jactel et al. 2019)
    This article summarizes the uses, environmental and health risks of five neonicotinoid pesticides and assesses alternatives for pest management within the context of recent European regulatory restrictions. Each alternative is examined with reference to efficacy in controlling target pests and adverse effects on non-target species and the environment. The investigators found that in 96% of cases replacements can be found and in 78% of cases at least one chemical alternative exists.
  • Trends in neonicotinoid pesticide residues in food and water in the United States, 1999–2015 (Craddock 2019)
    This article utilizes data from the US Department of Agriculture’s Pesticide Data Program to examine trends in residue concentrations in commonly consumed produce in the U.S. Although low levels are found, use of certain compounds is rising. Increased surveillance, biomonitoring studies and a focus on high risk groups is recommended.
  • Potential human exposures to neonicotinoid insecticides: A review (Zhang et al, 2018)
    This review of articles on human exposure and biomonitoring published prior to 2017 indicated there is risk of neonicotinoids exposure, given that they are ubiquitous and have long half-lives.
  • Neonicotinoid residues in fruits and vegetables: An integrated dietary exposure assessment approach (Lu et al., 2018)
    This cross-sectional study analyzed residues of seven neonicotinoids in fruit and vegetable samples collected from U.S. and Chinese studies. Imidacloprid and thiamethoxam were detected in over one half of the samples. The authors concluded that neonicotinoids have become part of the dietary staple, with possible health implications for individuals.
  • Catching up with popular pesticides: More human health studies are needed on neonicotinoids (Seltenrich, 2017)
    This science selection article emphasizes the widespread use of neonicotinoids and the concern that these insecticides can have adverse effects on mammals at sublethal doses, which suggests there is the potential for human health effects.
  • Human exposure to neonicotinoid insecticides and the evaluation of their potential toxicity: An overview (Han et al., 2017)
    This narrative review refers to studies on human neonicotinoid exposure levels and health effects, and provides an evaluation of the potential toxicity of neonicotinoids on humans.

This list is not intended to be exhaustive. Omission of a resource does not preclude it from having value.

What Are Neonicotinoids Pesticides And How Do Neonicotinoids Work

We’ve all heard a little something about the bird and the bees, but have you heard mention of neonicotinoids and bees? Well, hold on to your hat because this important information could mean the life and death of our precious pollinators in the garden. Keep reading to learn more about neonicotinoids killing bees and what we can do about it.

So the first question that needs to be clarified, obviously, is “what are neonicotinoids?” If you haven’t heard this term, that’s probably due to the fact that it’s a relatively new class of synthetic insecticides. Neonicotinoid pesticides (aka neonics) are similar to nicotine, which is naturally found in nightshade plants like tobacco, and supposedly less harmful to humans but is poisonous to bees and many other insects and animals.

These types of insecticides affect the central nervous system of insects, resulting in paralysis and death. Among them includes:

  • Imidacloprid – considered the most popular neonicotinoid, you’ll find it listed under the trade names Merit®, Admire®, Bonide, Ortho Max and some of the Bayer Advanced products. While listed as moderately toxic, it has been found highly toxic to bees and other beneficial insects.
  • Acetamiprid – even with its low acute toxicity, this one has shown population-level effects on honeybees.
  • Clothianidin – this is a neurotoxic and is highly toxic to bees and other non-target insects.
  • Dinotefuran – commonly used as a broad spectrum of insects infesting cotton and vegetable crops.
  • Thiacloprid – although targeted to control sucking and biting insects, low doses are highly toxic to honeybees, and also causes physiological problems in fish when used within aquatic environments.
  • Thiamethoxam – this systemic insecticide is absorbed and transported to all parts of the plant and while considered moderately toxic, it’s harmful to bees, aquatic and soil organisms.

Studies have shown that residues from neonicotinoids pesticides can accumulate in the pollen of treated plants, posing a real danger to pollinators even after use of the pesticide stops on the plant.

How Do Neonicotinoids Work?

The EPA classifies neonicotinoids as both toxicity class II and class III agents. They are generally labeled with a “Warning” or “Caution.” Because the neonicotinoid pesticides block specific neurons in insects, they are deemed less harmful to warm-blooded animals but are highly toxic to insect pests as well as beneficial species like bees.

Many commercial nurseries treat plants with neonicotinoid pesticides. The chemical residue left behind from these treatments remain in nectar and pollen that gets collected from the bees, which is fatal. Unfortunately, research suggests that even if you treat these plants using organic approaches once purchased, the damage is already done, as the residue is still present. Therefore, neonicotinoids killing bees is inevitable.

Of course, an insecticide does not have to kill in order to have an effect. Research has indicated that exposure to neonicotinoids can interfere with honeybee reproduction and their ability to navigate and fly.

Neonicotinoids Alternatives

That being said, when it comes to neonicotinoids and bees (or other beneficials), there are options.

One of the best ways to keep harmful products out of the garden is to buy only organically grown plants. You should also purchase organic seeds or start your plants, trees, etc. from cuttings which have not been exposed to any chemicals and then continue using organic approaches throughout their lifetime.

Sometimes the use of pesticides becomes necessary. So when using insecticides, common sense goes a long way. Always read and follow the label directions carefully, and appropriately. Also, you might want to pay attention to the LD50 rate before you buy. This is the amount of chemical it takes to kill 50% of a test population. The smaller the number, the more toxic it is. For instance, according to one resource in the case of a honeybee, the amount of imidacloprid that must be ingested to kill 50% of the test subjects is 0.0037 micrograms compared to carbaryl (Sevin), which requires 0.14 micrograms – meaning the imidacloprid is far more toxic to bees.

This is something to keep in mind before using any insecticide, including neonicotinoids. Weigh your options carefully and, if you have determined that an insecticide is still necessary, consider the least toxic options first, such as insecticidal soap or neem oil.

Also, take into account whether or not plant needing treatment is flowering and attractive to bees. If the plant is blooming, consider waiting to treat once it has finished and is less attractive to bees and other pollinating insects.

The DDT and Rachel Carson

In recent years, the idea of a world without bees has transcended numerous social and political spheres. The scientific community has been warning about the disappearance of bees during years without any consequence. But now, it has become an issue of major concern, acquiring a media relevance like never before. At the end of 2017, the EU decided to take matters into its own hands to prevent this tragic ending for bees.

Why would it be a problem that bees disappear from Earth? And which measures has the UE take in order to address this problem?

The use of pesticides has been a common agricultural practice from the very beginning of agriculture. At the beginning, the use of organic chemicals derived from naturals sources, as well as inorganic substances such as sulphur, mercury and arsenical compounds, was very common. However, they eventually stopped being used due to their toxicity (especially, phytotoxicity). The growth in synthetic pesticides accelerated in the mid-twentieth century, especially with the discovery of the effects of DDT, which became one of the most widely used pesticides of all time. DDT became famous due to its generalist insecticidal effects and low toxicity to mammals and plants, being used to eradicate household pests, fumigate gardens and control agricultural pests.

Picture above: cover of a March 1947 brochure on DDT from the U.S. Department of Agriculture (source). Picture below: kids being showered with DDT during a campaing against poliomyelitis, which was believed to be transmitted by a mosquito (source).

DDT resulted to be very effective against insect vectors of deadly diseases such as malaria, yellow fever and typhus, thus becoming even more popular.

However, the overuse of this and other pesticides eventually began to cause severe human and environmental health problems, because some of these products started to contaminate soils, plants and their seeds, and to bioaccumulate within the trophic nets, finally affecting mammals, birds and fishes, among others. The indiscriminate use of pesticides and their effects were denounced by Rachel Carson through her most famous publication, “Silent Spring”, which was distributed in 1962.

Silent Spring, by Rachel Carson (source).

From Carson to the neonicotinoids

Since Carson denounced the abusive use of pesticides, the world has witnessed the birth of many new substances to fight crop pests. Since then, researches have focused on finding less toxic and more selective products in order to minimize their impact on both human and environmental health. Could we say it has been a success?

Yes… and no. Although their use stopped being so indiscriminate and famers started betting on the use of more selective products, there were still some open fronts. Fronts that would remain open until today.

Between 1980 and 1990, Shell and Bayer companies started working on the synthesis of a new assortment of pesticides to face the resistances that some insects have acquired to some of the most widely used substances those days: the neonicotinoids. Neonicotinoids are a class of neuro-active insecticides chemically similar to nicotine; they effect the insect nervous system with a high specificity, while having a very low toxicity to mammals and birds compared to their most famous predecessors (organochlorides, such as the DDT, and carbamates). The most widely used neonicotinoid nowadays (and also one of the most widely used pesticides worldwide) is the imidacloprid.

However, far from getting famous for their effectiveness, the use of neonicotinoids began to get controversial for their supposed relationship with the disappearance of bees.

How do these pesticides affect bees?

For some years now (2006 onwards) the neonicotinoids are in scientists’ spotlight as one of the main suspects of the disappearance of bees. However, it has not been until now that something that scientists had been denouncing for years has finally been assumed: that neonicotinoids cause a greater impact than it was thought.

Dead bees in front of a hive. Public domain.

Unlike other pesticides that remain on plant surfaces, some studies state that neonicotinoids are taken up throughout their tissues, thus being accumulated in their roots, leaves, flowers, pollen and nectar. Also, that nearby fields are polluted with the dust created when treated seeds are planted and that plants derived from these seeds will accumulate a major amount of pesticide than sprayed plants (as it is explained in this publication of Nature). This causes bees (as well as other pollinating insects) to be exposed to high levels of pesticides, both in the crops themselves and in the surrounding foraging areas. These same studies have revealed with less support that these products may persist and accumulate in soils, which may affect future generations of crops.

Some of the negative effects on bees that have been related to neonicotinoids are:

  • Altered immune system, reduced overwintering success and reproduction in both honeybees and wild bees (according to this recent study published in Science).
  • Risk of disorientation in bees when looking for food (foraging habits) in both honeybees and wild bees, as well as communication disruption in colonial bees.
  • Enhanced negative effects by the interaction with other pesticides.
  • Contribution to the CCD (Colony Collapse Disorder). This phenomenon is characterized by the massive disappearance of worker bees from a colony, which leave behind the queen along with food, its larvae and some bees that take care of them. This phenomenon has been recorded numerous times throughout history; the last one occurred in the USA in 2006, when a large number of honey bee colonies (Apis mellifera) began to collapse (until 2013, about 10 million hives have disappeared, almost 2 times more than what is considered normal). The CCD is a multifactorial phenomenon, in which the action of pesticides seems to be only one of a long list of possible triggers.

In addition to the effects of neonicotinoids, other important causes must be taken into account: climate change, less food sources and changes in soil uses.

What would happen if bees disappear?

Colonial bees (like honeybees) are the most famous among bees. However, they only represent a mere portion within the great diversity of known bees, most of which have solitary life habits and build their nests inside small cavities. The ecological importance of solitary bees is equal to or greater than that of honey bees, but effects that neonicotinoids have on them are still poorly studied. Together, bees are among the most efficient pollinating organisms.

Solitary bee entering in its nest. Public domain.

According to this study carried out in German territory and published in POLS One at the end of 2017, a large part of flying insect diversity (including numerous pollinators) and up to 75% of their biomass have decreased in the last three decades due to the interaction of several factors. And if that was not enough, the authors say that these numbers can probably be extrapolated to other parts of the world.

What would happen if both colonial and solitary bees disappear?

  • Disappearance of crops. The production of many crops, such as fruit trees, nuts, spices and some oils, depends entirely on pollinators, especially on bees.
  • Decrease in the diversity and biomass of wild plants. Up to 80% of wild plants depend on insect pollination to reproduce, as it happens with many aromatic plants. A decrease in the vegetal surface would lead to serious problems of erosion and desertification.
  • Less recycling of soil nutrients. With the disappearance of the plants, the washing and deposition of soil nutrients would go down.
  • Less biological pest control. Some solitary bees are parasitoids of other solitary bees and other groups of insects (natural enemies); their absence could trigger the recurrence of certain pests.
  • Negative effects on higher trophic levels. The disappearance of bees could cause a decrease in the diversity and biomass of some birds that feed on pollinators.
  • Disappearance of bee-derived products, such as honey or wax.

The UE bans the use of neonicotinoids

Facing this reality, several governments have tried to limit the use of pesticides as a part of the measures to stop the decline of bee populations and the resulting economic losses. To give some examples, since 2006 the biomass of honey bees has decreased by 40% in the US, 25% in Europe since 1985 and 45% in the United Kingdom since 2010, according to data published by Greenpeace.

To date, the more restrictive measures limited the use of neonicotinoids in certain situations or seasons. But at the beginning of 2018, the EU, after preparing a detailed report based on more than 1,500 scientific studies carried out by the EFSA (European Food Safety Authority), decided to definitively ban the use of the three most used neonicotinoids in a maximum period of 6 months in all its member states after demonstrating that they are harmful for bees: imidacloprid, clothianidin and thiamethoxam.

Will the objectives of this report be accomplished? We will have to wait …

. . .

Although slowly, the fight against the abusive use of pesticides is paying off. However, we will have to see if the gap left by some products is filled with other substances or if governments commit to adopt more environment friendly agricultural models.

Main picture obtained from .

New Evidence Shows Popular Pesticides Could Cause Unintended Harm To Insects

Honeybees are seen feeding on the honeydew of whiteflies in citrus trees. Traces of neonicotinoids, a family of pesticides, have shown up in honeydew, an important food source for other insects. Alejandro Tena hide caption

toggle caption Alejandro Tena

Honeybees are seen feeding on the honeydew of whiteflies in citrus trees. Traces of neonicotinoids, a family of pesticides, have shown up in honeydew, an important food source for other insects.

Alejandro Tena

Consider, for a moment, the circuitous journey of the insecticide called thiamethoxam, on its way to killing a wild wasp.

Alejandro Tena, a researcher at the Valencia Institute of Agricultural Research, in Spain, mixed the chemical into water used to irrigate clementine trees. This is a common practice among citrus farmers. As intended, the tree roots absorbed the insecticide, and it spread throughout the trees’ branches and leaves.

A mealybug landed on the clementine tree, bit through the bark, and began feeding on tree sap underneath. The bug ingested traces of the insecticide. This, in fact, is how thiamethoxam is supposed to work.

Unfortunately, though, the pesticide’s journey wasn’t over. Traces of it showed up in a sticky, sugary, substance called honeydew that the mealybugs excrete. Honeydew is an important food for other insects, such as wasps and hoverflies. In Tena’s experiments, wasps and hoverflies that fed on this contaminated honeydew died in large numbers. Wasps and hoverflies are a fruit grower’s friends, because they help to fight harmful insects.

Tena’s study, published this week in the Proceedings of the National Academy of Sciences, is just the latest evidence that a family of pesticides called neonicotinoids, sometimes just called “neonics,” can pose risks to the insect world that are not fully understood.

“This is the problem with water-soluble pesticides like neonics,” says Christian Krupke, an entomologist at Purdue University. “It’s very hard to predict where they’ll go and what will happen when they’re out in the environment.” Other studies have shown that neonicotinoids that are absorbed by crops and wildflowers can later show up in the plants’ nectar and pollen, affecting bees and other pollinators. A few years ago, scientists found that slugs living in the soil were ingesting neonics and thus poisoning slug-eating beetles.

Neonicotinoids are deadly to a wide range of insects, but they are relatively safe for people and other mammals; much safer, for instance, than an older family of insecticides called organophosphates. In recent years, farmers have rapidly increased their use of neonics. Most corn and soybean seeds that are planted in the United States now come pre-coated with them.

Another study published this week argues that this shift has made American agriculture dramatically more toxic for insects.

The authors of the study came up with a new way to measure the potential impact of various insecticides, taking into account both the level of toxicity and how long the chemicals persist in the environment.

According to this new measure of “toxicity loading,” U.S. agriculture is now 48 times as deadly to insects as it was a quarter-century ago, before neonicotinoids were introduced.

Kendra Klein, a senior staff scientist at Friends of the Earth who co-authored the new study, said in a news release that “we need to phase out neonicotinoid pesticides to protect bees and other insects that are critical to biodiversity.” The study appears in the journal PLOS One.

The companies Bayer and Syngenta, which make neonicotinoids, downplayed the significance of the new studies. Syngenta said in a statement that Tena’s observation of neonic-laced honeydew killing beneficial insects “is not indicative of real-world exposure.” The company pointed out that in this experiment, wasps and hoverflies were only permitted to feed on honeydew from thiamethoxam-treated trees, increasing their exposure. According to Syngenta’s statement, “in the real world, there would be other food sources, such as nectar and honeydew from untreated plants.”

Bayer’s director of pollinator safety, David Fischer, wrote in a statement that neonicotinoids “are typically applied in a way that limits exposure to honey bees and other non-targets.” Most neonicotinoids are not sprayed directly on plants, but are instead used as coatings on seeds. When the seeds are planted, the neonics are trapped in the soil. Only small amounts reach insects living above ground, for instance, when aphids feed on plants treated with the chemicals.

Krupke, from Purdue University, wrote in an email to The Salt that since most neonics remain in the soil, their impact on soil-dwelling insects deserves more attention. Earthworms, for instance, are sensitive to neonicotinoids. “We just don’t know enough about the soil residents to say with certainty” what the effects are,” he wrote.

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