Clothianidin
Clothianidin 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 that are chemically similar to nicotine, which has been used as a pesticide since the late 1700s. Clothianidin and other neonicotinoids act on the central nervous system of insects as an agonist of nAChR, the same receptor as acetylcholine, the neurotransmitter that stimulates and activating post-synaptic acetylcholine receptors but not inhibiting AChE. Clothianidin and other neonicotinoids were developed to last longer than nicotine, which is more toxic and which breaks down too quickly in the environment.
A 2018 review by the European Food Safety Authority concluded that most uses of neonicotinoid pesticides such as clothianidin represent a risk to wild bees and honeybees. In 2022 the United States Environmental Protection Agency concluded that clothianidin is likely to adversely affect 67 percent of federally listed endangered or threatened species and 56 percent of critical habitats. The pesticide has been banned for all outdoor use in the entire European Union since 2018, but has a conditional approval in the U.S. and other parts of the world, where it is widely used.
Clothianidin is an alternative to organophosphate, carbamate, and pyrethroid pesticides. It poses lower risks to mammals, including humans, when compared to organophosphates and carbamates. It has helped prevent insect pests from building up resistance to organophosphate and pyrethroid pesticides.
Authorized uses
Clothianidin is authorized for spray, dust, soil drench, injectable liquid, and seed treatment uses, in which clothianidin coats seeds that take up the pesticide via the roots as the plant grows. The chemical may be used to protect plants against a wide variety of agricultural pests in many countries, of which the following are mentioned in citable English-language sources: Australia, Austria, Belgium, Bulgaria, Canada, Czech Republic, Denmark, Estonia, France, Finland, Germany, Greece, Hungary, Italy, Ireland, Japan, Korea, Lithuania, Netherlands, New Zealand, Poland, Portugal, Serbia, Slovakia, Slovenia, Spain, UK, and the United States. Seed treatment uses of clothianidin, corn in particular, have been revoked or suspended in Germany, Italy and Slovenia. The suspensions are reflective of E.U. pesticide law and are generally associated with acute poisoning of bees from pesticide dust being blown off of treated seeds, especially corn, and onto nearby farms where bees were performing pollinator services.Clothianidin was prequalified for indoor residual spraying by the World Health Organization in 2017.
Background
Although nicotine has been used as a pesticide for over 200 years it degraded too rapidly in the environment and lacked the selectivity to be very useful in large-scale agricultural situations. However, in order to address this problem, the neonicotinoids were developed as a substitute of nicotine. Clothianidin is an alternative to organophosphate, carbamate, and pyrethroid pesticides. It poses lower risks to mammals, including humans, when compared to organophosphates and carbamates. It also plays a key role helping to prevent the buildup in insect pests of resistance to organophosphate and pyrethroid pesticides, which is a growing problem in parts of Europe.Clothianidin was first given registration for use as a pesticide by the Japan Plant Protection Association in 2001. Followed by conditional registration by the United States Environmental Protection Agency in 2003, pending the completion of additional study of its safety to be done by December 2004. Bayer did not complete the study on time and asked for an extension. The date was postponed to May 2005 and they also granted Bayer the permission it had sought to conduct its study on canola in Canada, instead of on maize in the United States. The study was not completed until 2007. In a November 2007 memo EPA scientists declared the study “scientifically sound,” adding that it, “satisfies the guideline requirements for a field toxicity test with honeybees.”
Clothianidin continued to be sold under a conditional registration, and in April 2010 it was granted an unconditional registration for use as a seed treatment for corn and canola. However, in response to concerns raised by bee keepers, in November the EPA released a memorandum in which they stated that some of the studies submitted did not appear to be adequate and the unconditional registration was withdrawn.
Toxicity
Regulatory authorities describe the toxicological database for clothianidin as "extensive", and many studies have been reviewed to support registrations around the globe for this chemical. Laboratory and field testing revealed that clothianidin shows relatively low toxicity to many test species but is highly or very highly toxic to others. Toxicity varies depending on whether the exposure occurs on a short-term or long-term basis.Bees and other insect pollinators
s pollinate crops responsible for about a third of the human diet; about $224 billion worth of crops worldwide. Beginning in 2006, beekeepers in the United States began to report unexplained losses of hives — 30 percent and upward — leading to a phenomenon called colony collapse disorder. The cause of CCD remains under debate, but scientific consensus is beginning to emerge suggesting that there is no one cause but rather a combination of factors including lack of foraging plants, infections, breeding, and pesticides—with none catastrophic on their own, but having a synergistic effect when occurring in combination.The Australian Pesticides and Veterinary Medicines Authority notes that clothianidin ranks "among the most highly acutely toxic insecticides to bees" through contact and oral exposure. Since clothianidin is a systemic pesticide that is taken up by the plant, there is also potential for toxic chronic exposure resulting in long-term effects to bees and other pollinators from clothianidin residue in pollen and nectar. According to the Environmental Protection Agency, in addition to potential effects on worker bees, there are also concerns about lethal and/or sub-lethal effects in the larvae and reproductive effects in the queen from chronic exposure. However, in a 2012 statement the EPA reported that they are not aware of any data demonstrating that bee colonies are subject to elevated losses due to long-term exposure when clothianidin products are used at authorized rates.
Honey bees and other pollinators are particularly sensitive to clothianidin, as evidenced by the results of laboratory and field toxicity testing and demonstrated in acute poisoning incidents in France and Germany in 2008, and in Canada in 2010 and 2013 associated with the planting of corn seeds treated with clothianidin. To reduce the risk to pollinators from acute exposure to clothianidin sprays, label instructions prohibit the use of these products when crops or weeds are in bloom and pollinators are nearby, but in the U.S. label instructions do not require the use of a "sticker", a sticking agent meant to reduce dust from treated seeds during planting. However, according to the EPA, the use of sticking agents to reduce dust from treated seeds is standard practice in the U.S.
In a July 2008 German beekill incident, German beekeepers reported that 50 to 100 percent of their hives had been lost after pneumatic equipment used to plant corn seed blew clouds of pesticide dust into the air, which was then pushed by the wind onto neighboring canola fields in which managed bees were performing pollinator services. The accident was found to be the result of improper planting procedures and the weather. However, in 2009, Germany suspended authorization for the use of clothianidin on corn, citing unanswered questions that remained about potential exposure of bees and other pollinators to neonicotinoid pesticides.
A 2011 Congressional Research Report describing some of the reasons why scientists believe honey bee colonies are being affected by CCD reported that the United States Department of Agriculture had concluded in 2009, "it now seems clear that no single factor alone is responsible for the malady." According to the research report, the neonicotinoids, which contain the active ingredient imidacloprid, and similar other chemicals, such as clothianidin and thiamethoxam, are being studied for a possible link to CCD. Honey bees are thought to possibly be affected by such chemicals, which are known to work their way through the plant up into the flowers and leave residues in the nectar and pollen that bees forage on. The scientists studying CCD have tested samples of pollen and have indicated findings of a broad range of substances, including insecticides, fungicides, and herbicides. They note that the doses taken up by bees are not lethal, but they are concerned about possible chronic problems caused by long-term exposure.
A report released in 2012 found a close relationship between the deaths of bees and the use of pneumatic drilling machines for the sowing of corn seeds coated with clothianidin and other neonicotinoid insecticides. In pneumatic drilling machines, seeds are sucked in, causing the erosion of fragments of the insecticide shell, which are then expelled with a current of air. Field tests found that foraging bees flying through dust released during the planting of corn seeds coated with neonicotinoid insecticides may encounter exposure high enough to be lethal. They concluded: "The consequent acute lethal effect evidenced in all the field sowing experiments can be well compared with the colony loss phenomena widely reported by beekeepers in spring and often associated to corn sowing." Another field study released in 2012 looked at sublethal effects of clothianidin and imidacloprid in amounts that bees might be exposed to during foraging. Sublethal doses can affect orientation, foraging, learning ability and brood care. The study found: "clothianidin elicited detrimental sub-lethal effects at somewhat lower doses than imidacloprid. Bees disappeared at the level of 1 ng for clothianidin, while we could register the first bee losses for imidacloprid at doses exceeding 3 ng."
In a 2012 study, scientists found that an analyses of bees found dead in and around hives from several apiaries in Indiana showed the presence of the neonicotinoid insecticides clothianidin and thiamethoxam. The research showed that the insecticides were present at high concentrations in waste talc that was exhausted from farm machinery during planting and that is left outside after cleaning the planting equipment. Talc is used in the vacuum system planters to keep pesticide treated seeds flowing freely and was studied by the investigators since the waste talc can be picked up by the wind, and could spread the pesticide to non-treated areas; they did not however investigate whether and how much pesticide spreads this way. The insecticides were also consistently found at low levels in soil up to two years after treated seed was planted, and on nearby dandelion flowers and corn pollen gathered by the bees. Also in 2012, researchers in Italy published findings that the pneumatic drilling machines that plant corn seeds coated with clothianidin and imidacloprid release large amounts of the pesticide into the air, causing significant mortality in foraging honey bees.
Studies have shown that milkweed plants contaminated with clothianidin can have a detrimental effect on the development and survival of monarch butterfly caterpillars.