Neonicotinoids
Encyclopedia
Neonicotinoids are a class of insecticide
s which act on the central nervous system
of insects with lower toxicity to mammals. Neonicotinoids are among the most widely used insecticides worldwide, but recently the uses of some members of this class have been restricted in some countries due to a possible connection to honey-bee colony collapse disorder
, though no scientific evidence has been established confirming that connection.
, and there are no records of cross-resistance
to the carbamate
, organophosphate
, or synthetic pyrethroid
insecticides, thus making them important for management of insecticide resistance. As a group they are effective against sucking insects such as aphids, but also chewing insects such as Coleoptera and some Lepidoptera
.
All of the neonicotinoids were registered after 1984 and were not subject to reregistration. Some uncertainties have been identified since their initial registration regarding the potential environmental fate and effects of neonicotinoid pesticides, particularly as they relate to pollinators. Some of the compounds within this class have been demonstrated to persist for several years and residues have been detected in plants for several years following application. Studies conducted in Europe in the late 1990s have suggested that neonicotinic residues can accumulate in pollen and nectar of treated plants and represent a potential risk to pollinators. Adverse effects on pollinators (beekill incidents) have also been reported in Europe that have further heightened concerns regarding the potential direct and/or indirect role that neonicotinic pesticides may have in pollinator declines, though no evidence of a link to such incidences has been established. Recently submitted registrant data from studies conducted in Europe have supported concerns regarding the persistence of neonicotinoids; however, the translocation of residues into pollen and nectar of treated plants and the potential effect that these residues may have on bees remains uncertain.
According to the United States Environmental Protection Agency
registration review docket for imidacloprid opened in December 2008, and the docket for nithiazine opened in March 2009. To better ensure a “level playing field” for the neonicotinoid class as a whole, and to best take advantage of new research as it becomes available, the EPA has moved the docket openings for the remaining neonicotinoids on the registration review schedule (acetamiprid, clothianidin, dinotefuran, thiacloprid and thiamethoxam) to 2012.
is possibly the most widely used insecticide, both within the mode of action group and in the worldwide market. It is now applied against soil, seed, timber and animal pests as well as foliar treatments for crops including: cereals, cotton, grain, legumes, potatoes, pome fruits, rice, turf and vegetables. It is systemic with particular efficacy against sucking insects and has a long residual activity. The application rates for neonicotinoid insecticides are much lower than older, traditionally used insecticides.
Thiamethoxam
(TMX) is a second generation neonicotinoid insecticide, belonging to the thianicotinyl subclass. Thiamethoxam's chemical structure is slightly different from other neonicotinoid insecticides, making it highly water soluble and therefore readily translocated in plant tissue. TMX is systemic and penetrates into the plant cells where it also triggers various physiological reactions, which induce the expression of specific functional proteins involved in various stress defense mechanisms of the plant allowing it to better cope under tough growing conditions, such as:
In 2001, the US Patent and Trademark Office ruled in favor of Syngenta
when the company filed suit against Bayer
to protect its patent on a class of neonicotinoid insecticides.
and imidacloprid effects on bee population
. Neonicotinoid use has been strictly limited in France since the 1990s, when neonicotinoids were implicated in a mass die-off of the bee population. It is believed by some to account for worker bees' neglecting to provide food for eggs and larvae, and for a breakdown of the bees' navigational abilities, possibly leading to what has become generally known as Colony Collapse Disorder
.
It was banned in Slovenia
in 2003 due to Colony Collapse Disorder
. Its usage has later been allowed, but microbiology experts believe the decision was based on a quick and incomplete government research by the ministry and was influenced by Monsanto
, an agricultural biotechnology company. Independent studies show that while the photodergradation half-life time of most neonicotinoids is around 34 days when exposed to sunlight, it might take up to 1386 days for these compounds to degrade in the absence of sunlight and microorganism activity. Some activists are concerned that neonicotinoids applied agriculturally might accumulate in aquifer
s.
In 2008 Germany revoked the registration of clothianidin for use on seed corn after an incident that resulted in the death of hundreds of nearby honey bees. Investigation of the incident revealed that it was caused by a combination of factors, among which were the failure to use a polymer seed coating known as a "sticker"; weather conditions that resulted in late planting when nearby canola
crops were in bloom; a particular type of air-driven equipment used to sow the seeds which apparently blew clothianidin-laden dust off the seeds and into the air as the seeds were ejected from the machine into the ground; dry and windy conditions at the time of planting that blew the dust into the nearby canola fields where honey bees were foraging.; and a higher application rate which had been authorized for a severe root worm infestation. Clothianidin was also restricted for a short period for use on rapeseed
; however, after evidence had shown that the problems resulting from maize
seed were not transferable to rapeseed, its use was reinstated under the condition that the pesticide be fixed to the rapeseed grains by means of an additional sticker, so that abrasion dusts would not be released into the air.
In 2009 the German Federal Office of Consumer Protection and Food Safety decided to continue to suspend authorization for the use of clothianidin on corn because it has not yet been fully clarified to what extent and in what manner had bees come into contact with the active substances in the pesticides belonging to the neonicotinoid group (clothianidin, thiamethoxam
and imidacloprid
) when used on corn. In addition, on the basis of new findings, the question arose as to whether drops of liquid from plants which are taken in by bees pose an additional risk.
Neonicotinoid seed treatment uses are banned in Italy, but foliar uses are allowed. This action was taken based on preliminary monitoring studies showing that bee losses were correlated with the application of seeds treated with these compounds; Italy also based its decision on the known acute toxicity of these compounds to pollinators.
Sunflower and corn seed treatments of the active ingredient imidacloprid are suspended in France; other imidacloprid seed treatments, such as for sugar beets and cereals, are allowed, as are foliar uses.
The 2009 documentary Vanishing of the Bees
suggests that a link between neonicotinoid pesticides and colony collapse disorder
exists, although the experts interviewed indicated that analysis of the data does not confirm such a linkage.
On July 23, 2010, Dutch toxicologist, Dr Henk Tennekes had a scientific paper published in the journal, Toxicology (online) titled,Druckrey-Küpfmüller equation for risk assessment. He then authored and published a book in regards to his research called "A Disaster in the Making". The book explores the impact of neonicotinoids on the immune system of bees.
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
s which act on the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
of insects with lower toxicity to mammals. Neonicotinoids are among the most widely used insecticides worldwide, but recently the uses of some members of this class have been restricted in some countries due to a possible connection to honey-bee colony collapse disorder
Colony Collapse Disorder
Colony collapse disorder is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of...
, though no scientific evidence has been established confirming that connection.
Mode of action
The neonicotinoids are a class of insecticides with a common mode of action that affects the central nervous system of insects, causing paralysis and death. Under the WHO / EPA classification these compounds are placed toxicity class II or class III. Because the neonicotinoids block a specific neural pathway that is more abundant in insects than warm-blooded animals, these insecticides are selectively more toxic to insects than mammals. They bind at a specific site, the postsynaptic nicotinic acetylcholine receptorNicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction...
, and there are no records of cross-resistance
Cross-resistance
Cross-resistance is the tolerance to a usually toxic substance as a result of exposure to a similarly acting substance. It is a phenomenon affecting e.g. pesticides and antibiotics. As an example rifabutin and rifampin cross react in the treatment of tuberculosis. This sort of resistance is also...
to the carbamate
Carbamate
Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...
, organophosphate
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
, or synthetic pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...
insecticides, thus making them important for management of insecticide resistance. As a group they are effective against sucking insects such as aphids, but also chewing insects such as Coleoptera and some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
.
All of the neonicotinoids were registered after 1984 and were not subject to reregistration. Some uncertainties have been identified since their initial registration regarding the potential environmental fate and effects of neonicotinoid pesticides, particularly as they relate to pollinators. Some of the compounds within this class have been demonstrated to persist for several years and residues have been detected in plants for several years following application. Studies conducted in Europe in the late 1990s have suggested that neonicotinic residues can accumulate in pollen and nectar of treated plants and represent a potential risk to pollinators. Adverse effects on pollinators (beekill incidents) have also been reported in Europe that have further heightened concerns regarding the potential direct and/or indirect role that neonicotinic pesticides may have in pollinator declines, though no evidence of a link to such incidences has been established. Recently submitted registrant data from studies conducted in Europe have supported concerns regarding the persistence of neonicotinoids; however, the translocation of residues into pollen and nectar of treated plants and the potential effect that these residues may have on bees remains uncertain.
According to the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
registration review docket for imidacloprid opened in December 2008, and the docket for nithiazine opened in March 2009. To better ensure a “level playing field” for the neonicotinoid class as a whole, and to best take advantage of new research as it becomes available, the EPA has moved the docket openings for the remaining neonicotinoids on the registration review schedule (acetamiprid, clothianidin, dinotefuran, thiacloprid and thiamethoxam) to 2012.
Use
ImidaclopridImidacloprid
Imidacloprid is a nicotine-based, systemic insecticide, which acts as a neurotoxin and belongs to a class of chemicals called the neonicotinoids. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience,...
is possibly the most widely used insecticide, both within the mode of action group and in the worldwide market. It is now applied against soil, seed, timber and animal pests as well as foliar treatments for crops including: cereals, cotton, grain, legumes, potatoes, pome fruits, rice, turf and vegetables. It is systemic with particular efficacy against sucking insects and has a long residual activity. The application rates for neonicotinoid insecticides are much lower than older, traditionally used insecticides.
Thiamethoxam
Thiamethoxam
Thiamethoxam is an insecticide in the class of neonicotinoids. It has a broad spectrum of activity against many types of insects.-History:Thiamethoxam was developed by Syngenta but a patent dispute arose with Bayer which already had patents covering other neonicotinoids including imidacloprid...
(TMX) is a second generation neonicotinoid insecticide, belonging to the thianicotinyl subclass. Thiamethoxam's chemical structure is slightly different from other neonicotinoid insecticides, making it highly water soluble and therefore readily translocated in plant tissue. TMX is systemic and penetrates into the plant cells where it also triggers various physiological reactions, which induce the expression of specific functional proteins involved in various stress defense mechanisms of the plant allowing it to better cope under tough growing conditions, such as:
- Drought;
- Low pH;
- High soil salinity;
- Free radicals from UV radiation;
- Heat stress leading to protein degradation;
- Toxic levels of aluminum;
- Wounding from pests, wind, hail, etc., and;
- Virus attack.
In 2001, the US Patent and Trademark Office ruled in favor of Syngenta
Syngenta
Syngenta AG is a large global Swiss agribusiness company which notably markets seeds and pesticides. Syngenta is involved in biotechnology and genomic research. The company is a leader in crop protection, and ranks third in total sales in the commercial agricultural seeds market. Sales in 2010 were...
when the company filed suit against Bayer
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
to protect its patent on a class of neonicotinoid insecticides.
Environmental impact
There is controversy over the role of neonicotinoids in relation to pesticide toxicity to beesPesticide toxicity to bees
Pesticides vary in their effects on bees. Contact pesticides are usually sprayed on plants and can kill bees when they crawl over sprayed surfaces of plants or other media...
and imidacloprid effects on bee population
Imidacloprid effects on bee population
Imidacloprid is a systemic neonicotinoid insecticide produced by the German chemical firm Bayer CropScience and sold under such trade names as Gaucho, Admire, Merit, Advantage, Confidor, Provado, and Winner. It acts as a neurotoxin and interferes with the transmission of nerve impulses in insects...
. Neonicotinoid use has been strictly limited in France since the 1990s, when neonicotinoids were implicated in a mass die-off of the bee population. It is believed by some to account for worker bees' neglecting to provide food for eggs and larvae, and for a breakdown of the bees' navigational abilities, possibly leading to what has become generally known as Colony Collapse Disorder
Colony Collapse Disorder
Colony collapse disorder is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of...
.
It was banned in Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
in 2003 due to Colony Collapse Disorder
Colony Collapse Disorder
Colony collapse disorder is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of...
. Its usage has later been allowed, but microbiology experts believe the decision was based on a quick and incomplete government research by the ministry and was influenced by Monsanto
Monsanto
The Monsanto Company is a US-based multinational agricultural biotechnology corporation. It is the world's leading producer of the herbicide glyphosate, marketed in the "Roundup" brand of herbicides, and in other brands...
, an agricultural biotechnology company. Independent studies show that while the photodergradation half-life time of most neonicotinoids is around 34 days when exposed to sunlight, it might take up to 1386 days for these compounds to degrade in the absence of sunlight and microorganism activity. Some activists are concerned that neonicotinoids applied agriculturally might accumulate in aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s.
In 2008 Germany revoked the registration of clothianidin for use on seed corn after an incident that resulted in the death of hundreds of nearby honey bees. Investigation of the incident revealed that it was caused by a combination of factors, among which were the failure to use a polymer seed coating known as a "sticker"; weather conditions that resulted in late planting when nearby canola
Canola
Canola refers to a cultivar of either Rapeseed or Field Mustard . Its seeds are used to produce edible oil suitable for consumption by humans and livestock. The oil is also suitable for use as biodiesel.Originally, Canola was bred naturally from rapeseed in Canada by Keith Downey and Baldur R...
crops were in bloom; a particular type of air-driven equipment used to sow the seeds which apparently blew clothianidin-laden dust off the seeds and into the air as the seeds were ejected from the machine into the ground; dry and windy conditions at the time of planting that blew the dust into the nearby canola fields where honey bees were foraging.; and a higher application rate which had been authorized for a severe root worm infestation. Clothianidin was also restricted for a short period for use on rapeseed
Rapeseed
Rapeseed , also known as rape, oilseed rape, rapa, rappi, rapaseed is a bright yellow flowering member of the family Brassicaceae...
; however, after evidence had shown that the problems resulting from maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
seed were not transferable to rapeseed, its use was reinstated under the condition that the pesticide be fixed to the rapeseed grains by means of an additional sticker, so that abrasion dusts would not be released into the air.
In 2009 the German Federal Office of Consumer Protection and Food Safety decided to continue to suspend authorization for the use of clothianidin on corn because it has not yet been fully clarified to what extent and in what manner had bees come into contact with the active substances in the pesticides belonging to the neonicotinoid group (clothianidin, thiamethoxam
Thiamethoxam
Thiamethoxam is an insecticide in the class of neonicotinoids. It has a broad spectrum of activity against many types of insects.-History:Thiamethoxam was developed by Syngenta but a patent dispute arose with Bayer which already had patents covering other neonicotinoids including imidacloprid...
and imidacloprid
Imidacloprid
Imidacloprid is a nicotine-based, systemic insecticide, which acts as a neurotoxin and belongs to a class of chemicals called the neonicotinoids. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience,...
) when used on corn. In addition, on the basis of new findings, the question arose as to whether drops of liquid from plants which are taken in by bees pose an additional risk.
Neonicotinoid seed treatment uses are banned in Italy, but foliar uses are allowed. This action was taken based on preliminary monitoring studies showing that bee losses were correlated with the application of seeds treated with these compounds; Italy also based its decision on the known acute toxicity of these compounds to pollinators.
Sunflower and corn seed treatments of the active ingredient imidacloprid are suspended in France; other imidacloprid seed treatments, such as for sugar beets and cereals, are allowed, as are foliar uses.
The 2009 documentary Vanishing of the Bees
Vanishing of the Bees
Vanishing of the Bees is a 2009 documentary film by Hive Mentality Films & Hipfuel films, directed by George Langworthy and Maryam Henein and released in the United Kingdom on October 9. The story centers around the sudden disappearance of honey bees from beehives around the world, caused by the...
suggests that a link between neonicotinoid pesticides and colony collapse disorder
Colony Collapse Disorder
Colony collapse disorder is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of...
exists, although the experts interviewed indicated that analysis of the data does not confirm such a linkage.
On July 23, 2010, Dutch toxicologist, Dr Henk Tennekes had a scientific paper published in the journal, Toxicology (online) titled,Druckrey-Küpfmüller equation for risk assessment. He then authored and published a book in regards to his research called "A Disaster in the Making". The book explores the impact of neonicotinoids on the immune system of bees.
Active substances
Available neonicotinoid insecticides include:- AcetamipridAcetamipridAcetamiprid is an organic compound with the chemical formula C10H11ClN4. It is an odorless neonicotinoid insecticide produced under the trade names Assail,, and Chipco by Aventis CropSciences. It is systemic and intended to control sucking insects on crops such as leafy vegetables, citrus fruits,...
- ClothianidinClothianidinClothianidin is an insecticide developed by Takeda Chemical Industries and Bayer AG. Similar to thiamethoxam and imidacloprid, it is a neonicotinoid. Neonicotinoids are a class of insecticides which act on the central nervous system of insects with lower toxicity to mammals...
- DinotefuranDinotefuranDinotefuran is an insecticide of the neonicotinoid class developed by Mitsui Chemicals for control of insect pests such as aphids, whiteflies, thrips, leafhoppers, leafminers, sawflies, mole cricket, white grubs, lacebugs, billbugs, beetles, mealybugs, and cockroaches on leafy vegetables, in...
- ImidaclopridImidaclopridImidacloprid is a nicotine-based, systemic insecticide, which acts as a neurotoxin and belongs to a class of chemicals called the neonicotinoids. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience,...
- NitenpyramNitenpyramNitenpyram is an insecticide used in agriculture and veterinary medicine to kill insect external parasites of livestock and pets.In veterinary medicine, it is used orally with dogs and cats to control fleas . After ingestion, it begins killing fleas within 30 minutes and kills every adult flea on...
- ThiaclopridThiaclopridThiacloprid is an insecticide of the neonicotinoid class. Its mechanism of action involves disruption of the insect's nervous system by inhibiting nicotinic acetylcholine receptors. Thiacloprid was developed by Bayer CropScience for use on agricultural crops to control of a variety of sucking and...
- ThiamethoxamThiamethoxamThiamethoxam is an insecticide in the class of neonicotinoids. It has a broad spectrum of activity against many types of insects.-History:Thiamethoxam was developed by Syngenta but a patent dispute arose with Bayer which already had patents covering other neonicotinoids including imidacloprid...