Neonicotinoids were developed to find safer, more effective alternatives to chlorinated hydrocarbons, organophosphates, carbamates, and pyrethroids, so, ironically, some neonicotinoids are now banned in the EU because of their toxicity to bees and other pollinators, as well as to a wider group of species.
The agricultural and environmental consequences of neonicotinoid use and the recent EU regulatory restriction have made neonicotinoids one of the most controversial areas of science and policy.
A brief history of neonicotinoids and their use
Neonicotinoids – also known as neonics or NNIs – are a class of active substance used in crop protection products (CPPs) as an insecticide. They first appeared on the CPP market in the 1990s, and soon came to dominate it in the early 2000s.1
Neonicotinoids are systemic insecticides, meaning that they are taken up through the roots or leaves and translocated to other parts of the plant. They are toxic to herbivorous pests, providing direct protection from sap-sucking insects and indirect protection from plant viruses that are transmitted by insects.
Neonicotinoids were designed to offer advantages over existing insecticides, with potential advantages including;1
- Selective toxicity to arthropods over vertebrates
- High persistence
- Systemic activity
- Multiple modes of application that reduce operator exposure risks
- High water solubility, leading to the assumption of lower bioaccumulation and a lower impact on fish and other vertebrates.
- Neonicotinoids are valuable in agriculture because of their broad-spectrum activity against pests of economically important crops – from cereals to citrus fruit – and their versatile mode of application. The most common neonicotinoid application method is seed dressing, where it is applied prophylactically to the seeds and translocated through the plant as it grows. This can offer protection to seedlings for up to ten weeks and also reduce the need for subsequent multiple pesticide sprays.2
Concerns over neonicotinoid safety
The growth in neonicotinoid use occurred at roughly the same time as pollinator numbers, especially those of bees, started to decline in some countries, although the pattern was not consistent. This was the initial signal that led regulators to examine neonicotinoid safety, given the importance of bees to ecosystems and in sustaining commercial crop yields through pollination services.
As well as a direct impact on bee mortality, neonicotinoids have been shown to impact bee behavior and performance at sublethal doses. Behaviors impacted by neonicotinoids include memory, foraging efficiency, and queen production.3,4 The risk of exposure is dependent on neonicotinoid application rate, application method, and crop type.4
Many factors, other than pesticides, can impact bee health, including:
- Pests and pathogens: the varroa destructor mite has been linked to honey bee colony loss but, in addition, alien bee species spreading geographically also pose a threat to native bees
- Climate change: this can shift the normal distribution range of plants and pollinators, causing a mismatch in the synchronization of flowering and pollinator flight periods
- Reduced nutritional quality of forage: this is caused by reductions in flowering plant diversity and abundance, and an impact immunity, growth, and reproduction
- Loss/fragmentation of habitat: urbanization and intensification of farming have fragmented and reduced the areas used for bee nesting and foraging.
Regulation of neonicotinoids across the world
Regulators across the globe are concerned about the impact of neonicotinoids on bee health, although their responses have varied.
The US Environmental Protection Agency (EPA), US Department of Agriculture, and agencies in Canada and Australia, all state that neonicotinoids, as a seed treatment, are not a major health threat to honey bees. However, the US and Canadian governments both have a ‘Guidance for Assessing Pesticide Risks to Bees’6, and the EPA has issued a bee advisory box for labels to highlight its strengthened pollinator protection.
In the EU, three neonicotinoids – imidacloprid, clothianidin, and thiamethoxam – have had restrictions placed on their use, which are as follows:
- The use in bee-attractive crops (including maize, oilseed rape and sunflower) is prohibited, with the exception of uses:
- in greenhouses
- of treatment of some crops after flowering
- of winter cereals
- Applicants are obliged to provide ‘confirmatory information’ to confirm the safety of the uses still allowed.
Of the two other neonicotinoids currently approved in the EU, acetamiprid was assessed as being of low risk, and thiacloprid is already a candidate for substitution because of its endocrine disrupting properties.
Arguments related to the data underlying the European neonicotinoid restrictions
The European Food Safety Authority (EFSA) produced the risk assessment on the impact of neonicotinoids on which the European Commission (EC) based its legislation restricting/banning neonicotinoids. EFSA’s decision and the subsequent ban have been widely criticized by producers and farmers. The main criticisms have related to:
- The use of a draft guidance document – known as the Bee Risk Guidance Document (BRGD) – as the basis for the risk assessment, which set an unrealistically high safety bar that is difficult to overcome
- Risk assessments being made on the basis of tier I assessments, which are screening assessments usually used as triggers for higher-tier testing, while data from tier II and III testing were mostly absent
- Conclusions on the overall risk being misinterpreted.
How have the restrictions been applied at Member State level?
Member States (MSs) have used emergency authorizations, which are valid for 120 days, in situations where there is no reasonable protection against a pest other than neonicotinoids. In 2017, Bulgaria, Estonia, Finland, Hungary, Latvia, Lithuania, and Romania applied such emergency authorizations.8 EFSA, at the request of the EC, has now developed a methodology for evaluating the data supporting the use of emergency authorizations.9
Belgium issued an emergency 120-day authorization for thiamethoxam and clothianidin seed treatment of sugar beets, carrots and lettuce grown outdoors for the 2019 growing season. Belgium argued that use of low quantities of neonicotinoids, applied to seeds, avoids later foliar application of broad-spectrum pyrethroids, which are more hazardous to all beneficial arthropods. The risk to bees is minimized by the use of seed treatment, which does not cause dust drift, and as the crops do not flower or show guttation, exposure is limited. Further protection has been added by restricting crop rotation, so successive crops should be non-flowering or non-bee-attractive.
The consequence of the restriction on neonicotinoid use in the EU
There are concerns that the neonicotinoid ban, although designed to reduce one of the multiple stressors that bees are exposed to, may have consequences that could damage the wider ecological environment; for example, lower crop yields may encourage wider land use, which could impact biodiversity, and greater use of other, more toxic insecticides may have a wider effect on a broader set of species.
The debate on neonicotinoids in Europe has been polarized, which has made a balanced, reasoned debate difficult. The scientific research shows that neonicotinoids produce sub-lethal toxic effects in bees but that the risk is related to the way in which neonicotinoids are used. The consequences of a ban on neonicotinoid use may lead to other negative ecological effects, as well as economic ones for EU farmers. Balancing these conflicting opinions to ensure that bees, ecosystems, and agriculture are all protected is a massive and ongoing challenge.
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- Simon-Delso, N. et al. Systemic insecticides (Neonicotinoids and fipronil): Trends, uses, mode of action, and metabolites. Environ. Sci. Pollut. Res. 22, 5–34 (2015).
- King, A. What you need to know about neonicotinoids. Chemistry World (2018). Available at: https://www.chemistryworld.com/news/what-you-need-to-know-about-neonicotinoids/3008816.article
- Lamsa, J., Kuusella, E., Tuomi, J., Juntunen, S. & Watts, P. Low dose of neonicotinoid insecticide reduces foraging motivation of bumblebees. Proc. R. Soc. B Biol. Sci. 285, (2018).
- Wood, T. J. & Goulson, D. The environmental risks of neonicotinoid pesticides: a review of the evidence post-2013. Environ. Sci. Pollut. Res. Int. 24, 17285–17325 (2017).
- Entine, J. Global consensus finds neonicotinoids not driving honeybee health problems—Why is Europe so determined to ban them? Genetic Literacy Project (2018).
- USEPA. Guidance for Assessing Pesticide Risks to Bees. 59 (2014).
- Phytoweb. Neonicotinoids. Available at: https://fytoweb.be/en/plant-protection-products/use/neonicotinoids
- EFSA. Neonicotinoids: EFSA evaluates emergency uses. (2018). Available at: https://www.efsa.europa.eu/en/press/news/180621
- Grégoire, J. et al. Protocol for the evaluation of data concerning the necessity of the application of insecticide† active substances to control a serious danger to plant health which cannot be contained by other available means, including non‐chemical methods. EFSA Support. Publ. 14, 1–26 (2017).
- Trybou, M. Neonics to save bee(t)s! (2018). Available at: https://www.linkedin.com/pulse/neonics-save-beets-maarten-trybou/
- Noleppa, S. Banning neonicotinoids in the European Union: An ex-post assessment of economic and environmental costs. (2017).