Neonicotinoid

Neonicotinoids (sometimes shortened to neonics /ˈniːoʊnɪks/) are a class of neuro-active insecticides chemically similar to nicotine,^[1] developed by scientists at Shell and Bayer in the 1980s.^[2]

Neonicotinoids are among the widest-used insecticides in crop protection.^[3] They are also widely employed for veterinary purposes including tick and flea control.^[3] The first generation of neonicotinoids includes acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, nithiazine, thiacloprid and thiamethoxam. The more recently-marketed generation of neonicotinoids includes cycloxaprid, imidaclothiz, paichongding, sulfoxaflor, guadipyr and flupyradifurone.^[4] Imidacloprid has been the most widely used insecticide in the world from 1999^[5] through at least 2018^[update].^[6][7]

Because they affect the central nervous system of insects, neonicotinoids kill or deleteriously affect a wide variety of both target and non-target insects.^[8] They are often applied to seeds before planting as a prophylactic treatment against herbivorous insects. Neonicotinoids are water-soluble, so when the seed sprouts and grows, the developing plant absorbs the pesticide into its tissues as it takes in water.^[9] Neonicotinoids can also be applied to the soil directly.^[10] Once absorbed, neonicotinoids become present throughout the plant, including in its leaves, flowers, nectar, and pollen.^[8]

Neonicotinoid use has been linked to adverse ecological effects, including risks to many non-target organisms, and specifically on bees and pollinators.^[9][11][12] A 2018 review by the European Food Safety Authority (EFSA) concluded that most uses of neonicotinoid pesticides represent a risk to wild bees and honeybees.^[11][13] In 2022 the United States Environmental Protection Agency (EPA) concluded that neonicotinoids are likely to adversely affect the majority of federally listed endangered or threatened species and of critical habitats.^[12] Neonicotinoids widely contaminate wetlands, streams, and rivers, and due to their widespread use, pollinating insects are chronically exposed to them.^[14][15] Sublethal effects from chronic low-level exposure to neonicotinoids in the environment are thought to be more common in bees than directly lethal effects. These effects upon bees include difficulty navigating, learning, and foraging, suppressed immune response, lower sperm viability, shortened lifespans of queens, and reduced numbers of new queens produced.^[8]

In 2013, the European Union and some neighbouring countries restricted the use of certain neonicotinoids.^{[16][17][18][19][20][21]} In 2018 the EU banned the three main neonicotinoids (clothianidin, imidacloprid and thiamethoxam) for all outdoor uses.^[22][23] Several US states have restricted neonicotinoids out of concern for pollinators and bees.^[24]