Imidacloprid

Imidacloprid
IUPAC name N-[1-[(6-Chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl]nitramide
Identifiers
CAS number	138261-41-3 Y
PubChem	86418
ChemSpider	77934 Y
UNII	3BN7M937V8 Y
DrugBank	DB07980
KEGG	C11110 Y
ChEBI	CHEBI:39169 Y
ChEMBL	CHEMBL406819 Y
ATCvet code	QP53AX17
Jmol-3D images	Image 1
SMILES [O-][N+](=O)NC/1=N/CCN\1Cc2cnc(Cl)cc2
InChI InChI=1S/C9H10ClN5O2/c10-8-2-1-7(5-12-8)6-14-4-3-11-9(14)13-15(16)17/h1-2,5H,3-4,6H2,(H,11,13) Y Key: YWTYJOPNNQFBPC-UHFFFAOYSA-N Y InChI=1/C9H10ClN5O2/c10-8-2-1-7(5-12-8)6-14-4-3-11-9(14)13-15(16)17/h1-2,5H,3-4,6H2,(H,11,13) Key: YWTYJOPNNQFBPC-UHFFFAOYAZ
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)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Imidacloprid is a nicotine-based, systemic insecticide, which acts as an insect neurotoxin in certain insect species 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, (part of Bayer AG). It is sold under the trade names Kohinor, Admire, Advantage (Advocate) (flea killer for pets), Gaucho, Mallet, Merit, Nuprid, Optrol, Prothor, Turfthor, Confidor, Conguard, Dominion 2L, Hachikusan, Premise, Prothor, Provado, Intercept, Winner and Xytect. Imidacloprid is one of the most widely used insecticides. Approximately 95% of this compound is used on crops as a foliage spray. It also has many other valuable uses in the landscape and around the home. It has become a very important tool in the fight against the Emerald ash borer and the Asian long horned beetle. It's low cost and ease of application, along with its high efficacy make it invaluable. In trees it can be applied by soil injection or tree injection. It is also used as a topical application to the skin for lice in humans and for fleas and ticks on pets. Other application methods include: broadcast foliar or ground application as a granular or liquid formulation or as a pesticide-coated seed treatment.

Imidacloprid has been suspected of being associated with honeybee colony collapse disorder in man made hives. It has not however been directly linked to this disorder and research in recent years now points at other causes such as miticide sprays used by bee keepers to control mite parasites that are directly sprayed on the hive, a virus, and a fly known to parasitize American bumble bees and wasps has recently been discovered parasitizing California honey bees, causing bees to abandon their colonies in the night. Bees parasitized by the phorid fly became disoriented, "turning into zombies", flying out into the night to die the next day. Parasitism was widespread in the study area near the San Francisco Bay. Parasitism was found at 77% of the sites they investigated. The highest rate of parasitism was 91% of the nocturnally active bees at one site.

Over the past 20 years there has been much conjecture and guessing at the cause of bee die off in man made hives. And while imidacloprid has been pointed at by some, it must be recognized that research now points at other causes and that this epidemic was not happening everywhere imidacloprid was being used, but spread much like a disease spreads. Even in France, despite the widespread use of Imidacloprid, not all hives in all areas experienced die off at the same time. While a serious issue in some places in the 1990's, it did not become recognized to be a serious issue in the United States until the mid 2000's.

As a systemic pesticide, imidacloprid translocates or moves readily from the soil into the leaves, flowers, fruiting bodies, pollen, nectar, and guttation fluid of plants. Imidacloprid has limited mobility in the soil and does not bioaccumulate. For imidacloprid to be ingested in bees, it has to be translocated into plants and then the flowers where the bees can ingest it as they forage for pollen. Imidacloprid and other pesticides have been shown to weaken bees, making them more susceptible to parasites and other health issues. However, scientists no longer point directly at imidacloprid as the cause of this disorder. In fact despite banning imidacloprid and other neonicotonoids in France in 1999, Bee colony collapse disorder continues to be a serious issue. In Australia, where imidacloprid is widely used, there are no reports of colony collapse disorder, and there are also none of the viruses and mites that have also been linked as possible causes.

History

On January 21, 1986 a patent was filed, 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 March 25, 1992, Miles, Inc. (later Bayer CropScience) applied for registration of imidacloprid for turfgrass and ornamentals in the United States. On March 10, 1994, the U.S. Environmental Protection Agency approved the registration of imidacloprid.

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 (of) this pesticide on sunflower(s).

Biochemistry

Imidacloprid is a systemic chloronicotinyl pesticide, belonging to the class of neonicotinoid insecticides. It acts as a neurotoxin and interferes with the transmission of nerve impulses in insects by binding irreversibly to specific insect nicotinic acetylcholine receptors. [18]Interaction of Imidacloprid Metabolites and Analogues with the Nicotinic Acetylcholine Receptors of Mouse Brain in Relation to Toxicity. Chao and Casida 1997</ref>

As a systemic pesticide, imidacloprid translocates or moves easily in the xylem of plants from the soil into the leaves, fruit, pollen, and nectar of a plant. Imidacloprid also exhibits excellent translaminar movement in plants and can penetrate the leaf cuticle and move readily into leaf tissue. Since imidacloprid is efficacious at very low levels (nanogram and picogram), it can be applied at lower concentrations (e.g., 0.05–0.125 lb/acre or 55–140 g/ha) than other neurotoxins, particularly organophosphates.

The main routes of dissipation of imidacloprid in the environment are aqueous photolysis (half-life = 1–4 hours) and plant uptake. The major photo-metabolites include imidacloprid desnitro, imidacloprid olefine, imidacloprid urea, and five minor metabolites. The end product of photodegradation is chloronicotinic acid (CNA). Since imidacloprid has a low vapor pressure, it normally does not volatilize readily.

Imidacloprid is moderately soluble in water. It is not stable in water and in the presence of light breaks down rapidly. In water not in the presence of light, it's half life is longer. It does not bioaccumulate. In soil under aerobic conditions, imidacloprid has been shown to have half lives of 6 - 18 months. Ultimately, imidacloprid breaks into carbon dioxide. As it breaks down it transitions through metabolites that include imidacloprid nitrosimine, imidacloprid desnitro, hydroxynicotinic acid, and imidacloprid urea.

Both the U.S. Environmental Protection Agency and the Pest Management Regulatory Agency in Canada consider imidacloprid to have characteristic that give it potential to run off into surface water if used in flood plains and highly porous soils with very shallow ground water. In normal use however, runoff potential is virtually nil. When tested for in runoff during rain events, minuscule amounts have been detected. Typically in the .5 - 1 part per billion range. The EPA considers chronic exposure of 1770 ppb to be an issue.

Toxicology

Imidacloprid is toxic to honey bees with a contact acute LD₅₀ = 0.078 ug a.i./bee and an acute oral LD₅₀ = 0.0039 ug a.i./bee. Other systemic pesticides that have a higher acute toxicity to honey bees include clothianidin, thiamethoxam, dinotefuran, fipronil, emmamectin benzoate, and spinosad.

Researchers Kreutzweiser and Thompson (2009) from the Canadian Forest Service showed that imidacloprid at realistic field concentrations inhibits non-target terrestrial invertebrates that decompose leaf litter. In their study, there was no significant indication that invertebrates detected or avoided imidacloprid-treated leaves.

In bobwhite quail (Colinus virginianus), imidacloprid was determined to be moderately toxic with an acute oral LD₅₀ of 152 mg a.i./kg. These levels are much higher than would realistically be encountered. It was slightly toxic in a 5-day dietary study with an acute oral LC₅₀ of 1,420 mg a.i./kg diet, a NOAEC of < 69 mg a.i./kg diet, and a LOAEC = 69 mg a.i./kg diet. Exposed birds exhibited ataxia, wing drop, opisthotonos, immobility, hyperactivity, fluid-filled crops and intestines, and discolored livers. In a reproductive toxicity study with bobwhite quail, the NOAEC = 120 mg a.i./kg diet and the LOAEC = 240 mg a.i./kg diet. Eggshell thinning and decreased adult weight were observed at 240 mg a.i./kg diet.

Overdosage

Persons who might orally ingest acute amounts would experience emesis, diaphoresis, drowsiness and disorientation. This would need to be intentional since a large amount would need to be ingested to experience a toxic reaction. In dogs the LD₅₀ is 450 mg/Kg of body weight. 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., leafminers, some diptera, termites, locusts, and fleas).

As an insecticide spray, it is used on a wide variety of agricultural crops, ornamentals, and turf. It is also marketed for termite control, for flea control on pets, and for household cockroach control.

A systemic insecticide

Imidacloprid, which is a systemic pesticide, is readily taken up by plant roots and translocates up into the plant leaves, fruit, pollen, and nectar via the xylem. Insects that eat the leaves or plant fluids may be killed, and pollinators that feed on the pollen and nectar may be exposed to imidacloprid. 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.

Imidacloprid is the active ingredient in Bayer's Advantage brand flea drops.

See also

• Fipronil
• Imidacloprid effects on bees
• 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"