Imidacloprid

Imidacloprid
File:Imidacloprid.svg
IUPAC name N-[1-[(6-Chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl]nitramide
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	138261-41-3
PubChem	86418
ATCvet code	QP53AX17
SMILES
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C9H10ClN5O2
Molar mass	255.661
Appearance	Colorless crystals
Melting point	136.4-143.8 °C
Solubility in water	0.51 g/L (20 °C)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Imidacloprid is a neonicotinoid, which is a class of neuro-active insecticides modeled after nicotine. A patented chemical, imidacloprid is manufactured by Bayer Cropscience (part of Bayer AG) and sold under trade names Kohinor, Admire, Advantage(Advocate), Gaucho, Mallet, Merit, Nuprid, Prothor, Turfthor, Confidor, Hachikusan, Premise, Prothor, Provado and Winner. It is marketed as pest control, seed treatment, an insecticide spray, termite control, flea control, and a systemic insecticide.

Studies on rats indicate that the thyroid is the organ most affected by imidacloprid. Thyroid lesions occurred in male rats at a Lowest Observed Adverse Effect Level of 16.9 mg/kg/day

In France, its use (as Gaucho) has become controversial due to a possible link to derangement of behavior in domesticated honeybees. See Imidacloprid effects on bee population. In relation to this, Germany has banned seed treatment related to neonicotinoids, in May 2008, due to negative effects upon bee colonies.

History

On January 21, 1986 a patent was filed for, and granted on May 3, 1988 for, Imidacloprid in the United States (U.S. Pat. No. 4,742,060) by Nihon Tokushu Noyaku Seizo K.K. of Tokyo, Japan.

On January 26, 2005, the Federal Register notes the establishment of the '(Pesticide Tolerances for) Emergency Exemptions' for imidacloprid. It use was granted to Hawaii (for the) use (of) this pesticide on bananas(,) and the States of Minnesota, Nebraska, and North Dakota to use this pesticide on sunflower.

Biochemistry

A chlorinated analog of nicotine, the compound therefore belongs to the class of neonicotinoid insecticides, and acts on the nicotinic acetylcholine receptor; the chlorination inhibits degradation by acetylcholinesterase. Imidacloprid is notable for its relatively low toxicity to most animals other than insects due to its specificity for this type of receptor, which is found more often in insect nervous systems and zooplankton than that of other animals (exceptions exist, earthworms and a few species of fish, for example). This potentially allows for lower concentrations (e.g., 0.05–0.125 lb/acre or 55–140 g/ha) to be used for insect control than other neurotoxins (particularly organophosphates) and enables its use in applications as diverse as flea treatments for pets, control of beetle larvae in lawns, eradication or prevention of termite infestation in buildings, and other uses where animals and people may be exposed. Imidacloprid is, for example, present as a main (or the sole) active ingredient in concentrations between five and ten percent in three out of the four most widely used flea treatment and preventative topical treatments for dogs in the United States; these manufacturers claim an effective killing persistence of at least four weeks. The compound is also used for flea treatment on cats, whose livers have only limited detoxification ability compared with dogs and humans.

Imidacloprid has low vapor pressure. The chemical breaks down to inorganic molecules by both photolysis and microbial action. Photolysis in water results in a half-life of 1.4-10 days in water, while microbial action results in a half-life of 30-150 days in water/sediment systems and 106-193 days in soil. In soil under aerobic conditions, imidacloprid exhibits moderate to very high persistence. The manufacturer maintains that, when applied according to instructions, such long-term contamination is only found as the result of "repetitive application over several years" and its spread to populations of beneficial insects is minimal. In the body, 96% of the chemical is eliminated within 48 hours; the most important degradation product in the body is 6-chloronicotinic acid, another nicotinic neurotoxin with similar properties. Imidacloprid has, however, been reported to degrade into toxic, persistent, 2-chloropyridine.

Toxicology

Imidacloprid is rated as "moderately toxic" acutely by the World Health Organization and the United States Environmental Protection Agency‎ (class II or III, requiring a "Warning" or "Caution" label), and a "potential" ground water contaminant. It is rated as an "unlikely" carcinogen by the EPA (group E), and is not listed for endocrine, reproductive, or developmental toxicity, or as a chemical of special concern by any agencies. It is not banned, restricted, cancelled, or illegal to import in any country. It has, however, been banned for use as a crop pesticide in France since 1999. See Pesticide toxicity to bees. Tolerances for Imidacloprid residue in food range from 0.02 mg/kg in eggs to 3.0 mg/kg in hops.

Animal toxicity is similar to that of the parent compound, nicotine exhibited as fatigue, twitching, cramps, and weakness leading to asphyxia. The oral LD₅₀ of imidacloprid is 450 mg/kg body weight in rats and 131 mg/kg in mice; the 24-hour dermal LD₅₀ in rats is greater than >5000 mg/kg. It is not irritating to eyes or skin in rabbits and guinea pigs (although some commercial preparations contain clay as an inert ingredient, which may be an irritant). The acute inhalation LD₅₀ in rats was not reached at the greatest attainable concentrations, 69 milligrams per cubic meter of air as an aerosol, and 5,323 mg/m³ of air as a dust. In rats subjected to a two year feeding study, no observable effect was seen at 100 parts per million (ppm). At 300 ppm females showed decreased body weight gain and males showed increased thyroid lesions, while females showed increased thyroid lesions at 900 ppm. In a one-year feeding study in dogs, no observable effect was seen at 1,250 ppm, while levels up to 2,500 ppm led to hypercholesterolemia and elevated liver cytochrome p-450 measurements. Reproductive studies in rats resulted in no observable effect at 100 ppm and decreased pup weight at 250 ppm; developmental toxicity studies in rats showed no observable effect at 30 (mg/kg)/day and skeletal anomalies at 100 (mg/kg)/day, while in rabbits no observable effect was detected at 24 (mg/kg)/day and skeletal abnormalities at 72 (mg/kg)/day. Imidacloprid was negative for mutagenicity in 21 out of 23 different laboratory tests, but was positive for chromosomal changes in human lymphocytes and for genotoxicity in CHO cells. No carcinogenicity was seen in rats fed up to 1,800 mg/kg of imidacloprid for two years.

Overdosage

Persons who orally ingested acute overdoses experienced emesis, diaphoresis, drowsiness and disorientation. Blood imidacloprid concentrations may be measured to confirm diagnosis in hospitalized patients or to establish the cause of death in postmortem investigations.

Uses

The most widely used applications for imidacloprid in California are pest control in structures, turf pest control, grape growing, and head and leaf lettuce growing. Other widespread crop uses are rice, grains/cereals including corn (maize), potatoes, vegetables, sugar beets, fruit, cotton, and hops. Target insects include sucking insects (e.g., aphids, whiteflies, leafhoppers and planthoppers, thrips, scales, mealybugs, bugs, psyllids, and phylloxera), beetles (e.g., longhorn beetles, leaf beetles, Colorado potato beetles, rice water-weevils, wireworms, grubs, and flea beetles), and others (e.g., lepidopterous leafminers, some diptera, termites, locusts, and fleas).

As an insecticide spray, it is used on citrus, coffee, cotton, fruits, grapes, potatoes, rice, soybeans, sugarcane, tobacco and vegetables. It is also marketed for termite control, for flea control on pets, and for household cockroach control.

A systemic insecticide

Imidacloprid is taken up by plant roots and diffuses in the plant via the xylem; its systemic properties then rely on insects ingesting the insecticide (e.g., by sucking plant fluids). The products Confidor and Admire are intended for application via irrigation, application to the soil, or on foliage, while Gaucho is intended for use as a seed dressing, applied to the seed before sowing.

Seed-applied insecticides are often used to deal with numerous insects, as they are easy to use and comparable in cost to most traditional insecticides used at sowing time. Some also indicate that it might be better for the environment because less chemical is required than for broadcast or banded applications, or at least because less chemical is sprayed in the air. However, some note that the use of seed-applied insecticides at each season implies the chemical is used whether there is need to fight insects or not.

Imidacloprid is receiving increased attention as a possible factor in colony collapse disorder, a mysterious condition that causes sudden death of honey bee populations. Mass die-offs of bees threaten pollination of food crops in the USA and Europe.

Imidacloprid is the active ingredient in Bayer's Advantage brand flea and tick drops [1]

See also

• Fipronil
• Insecticide
• Neonicotinoid
• Pesticide toxicity to bees

Sources

• PAN Pesticides Database

External links

• Pesticide Information Profile from Extension Toxicology Network
• Breakdown Chart of Imidacloprid forming toxic 2-chloro pyridine
• Imidacloprid Fact Sheet, with 18 References, from the Sierra Club of Canada
• Bayer's "Expert Overview"

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