Description
Acephate(also known as Orthene) is a kind of organophosphate foliar insecticide which can be used for the treatment of leaf miners, caterpillars, sawflies and thrips in crops and aphides in vegetables and horticulture. It is one of the 10 most important organophosphate insecticides in the 1990s, and is still being widely used today. It takes effect through inhibiting the activity of acetylcholinesterase (Ache) after being metabolically converted to methamidophos. Since it can’t be converted to methamidophos, it is thought to cause no effect on animals and human beings.
Toxicity and health effects
Acephate is a colorless to white, solid organophosphate insecticide. Exposures to acephate cause poisoning to animals and humans. Acephate inhibits acetylcholine esterase (AchE), the essential nervous system enzyme, and causes characteristic organophosphate poisoning. The symptoms of toxicity include, but are not limited to, headache, nervousness, blurred vision, weakness, nausea, fatigue, stomach cramps, diarrhea, diffi culty breathing, chest pain, sweating, pin-point pupils, tearing, salivation, clear nasal discharge and sputum, vomiting, muscle twitching, muscle weakness, and in severe poisonings, convulsions,respiratory depression, coma, and death. Acephate causes cholinesterase inhibition leading to overstimulation, respiratory paralysis, and death.
Acephate and carcinogenicity
The US EPA classified acephate as Group C, meaning a possible human carcinogen.
References
[1] Mahajna, Mahmoud, G. B. Q. And, and J. E. Casida. "Acephate Insecticide Toxicity: Safety Conferred by Inhibition of the Bioactivating Carboxyamidase by the Metabolite Methamidophos." Chemical Research in Toxicology 10.1(1997): 64-9.
[2] Danka, Robert G., et al. "Doses and residues of acephate baits used to eradicate undesirable honey bees: A hazard assessment." Bulletin of Environmental Contamination & Toxicology 47.3(1991): 422.
[3] Wang, X., et al. "Environmental behavior of the chiral organophosphorus insecticide acephate and its chiral metabolite methamidophos: enantioselective transformation and degradation in soils. " Environmental Science & Technology 47.16(2013): 9233-9240.
[4] EXTOXNET. 1995. Acephate. Pesticide Information Profi les. Extension Toxicology Network. Cornell University, Ithaca, NY (updated 2001).
[5] Routt, R.J. and Roberts, J.R. 1999. Organophosphate insecticides. Recognition and Management of Pesticide Poisonings. US Environmental Protection Agency, National Technical Information Service (US EPA 735-R-98-003; pp. 55–57), Washington, DC.
[6] Tomlin, C.D.S. (ed.). 2008. The Pesticide Manual, 15th ed. British Crop Protection Council (BCPC). Blackwell Scientifi c, Hampshire, U.K.
US Environmental Protection Agency (US EPA). 1987. Acephate. Pesticide Fact Sheet. National Technical Information Service. US EPA, Washington, DC.
Description
Acephate is an organophosphate foliar spray insecticide of moderate persistence with residual
systemic activity. It is a contact and systemic insecticide and very effective against a large
number of crop pests such as alfalfa looper, aphids, armyworms, bagworms, bean leaf beetle,
bean leafroller, black grass bugs, bollworm, budworm, and cabbage looper. Acephate is a
colourless to white solid organophosphate insecticide. Exposures to acephate cause poisoning
to animals and humans. Acephate inhibits acetylcholine esterase (AchE), the essential nervous
system enzyme, and causes characteristic organophosphate poisoning. The symptoms
of toxicity include, but are not limited to, headache, nervousness, blurred vision, weakness,
nausea, fatigue, stomach cramps, diarrhoea, difficulty in breathing, chest pain, sweating,
pinpoint pupils, tearing, salivation, clear nasal discharge and sputum, vomiting, muscle
twitching, muscle weakness, and, in severe poisoning, convulsions, respiratory depression,
coma, and death. Acephate causes cholinesterase inhibition leading to overstimulation,
respiratory paralysis, and death. The U.S. EPA classified acephate as Group C, meaning a
possible human carcinogen, and therefore requires judicious handling and management.
Chemical Properties
Acephate is an organophosphate foliar spray insecticide of moderate persistence with
residual systemic activity. It is a contact and systemic insecticide and very effective against
a large number of crop pests, such as alfalfa looper, aphids, armyworms, bagworms, bean
leafbeetle, bean leafroller, blackgrass bugs, bollworm, budworm, and cabbage looper.
Chemical Properties
Colorless crystalline solid (80% or more pure) or white powder (technical). Has an odor of rotten cabbage or mercaptans (like sulfur).
Chemical Properties
White Solid
Uses
Acephate is used to control a wide range of sucking and chewing
insects in a large number of crops.
Uses
Contact and systemic insecticide for control of sucking and chewing insects in
cotton, ornamentals, forestry, tobacco, fruits, vegetables and other crops
Uses
Acephate is an organophosphate foliar spray insecticide of moderate persistence with residual systemic activity. It is a contact and systemic insecticide and very effective against a large number of crop pests, such as alfalfa looper, aphids, armyworms, bagworms, bean leafbeetle, bean leafroller, blackgrass bugs, bollworm, budworm, and cabbage looper.
Production Methods
Acephate is manufactured through a continuous chemical process that enhances efficiency and yield. The synthesis begins by reacting O,O-dimethyl phosphoroamidothioate with dimethyl sulfate to produce methamidophos, a key intermediate. This compound is then acetylated using an acetylating agent to form acephate.
Definition
ChEBI: A phosphoramide that is methamidophos in which one of the hydrogens is replaced by an acetyl group.
General Description
A white solid. Used as a contact and systemic insecticide.
Air & Water Reactions
Soluble in water.
Reactivity Profile
A thiophosphate ester. Organothiophosphates are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.
Health Hazard
Acephate is a colorless to white, solid organophosphate insecticide. Exposures to acephate
cause poisoning to animals and humans. Acephate inhibits acetylcholine esterase (AchE),
the essential nervous system enzyme, and causes characteristic organophosphate poi-
soning. The symptoms of toxicity include, but are not limited to, headache, nervousness,
blurred vision, weakness, nausea, fatigue, stomach cramps, diarrhea, diffi
culty breathing,
chest pain, sweating, pin-point pupils, tearing, salivation, clear nasal discharge and spu-
tum, vomiting, muscle twitching, muscle weakness, and in severe poisonings, convulsions, respiratory depression, coma, and death. Acephate causes cholinesterase inhibition lead-
ing to overstimulation, respiratory paralysis, and death.
Agricultural Uses
Insecticide: Acephate is a general use contact and systemic
insecticide. Not approved for use in EU countries.
Actively registered in the U.S., homeowner use for lawns
is discontinued except for treatment of fire ant mounds.
Other indoor treatment has been discontinued. Used on
green and lima beans, Brussels sprouts, cauliflower, celery, cotton, cottonseed, cranberries, head lettuce, macadamia nuts, peanuts, bell-and non-bell peppers, peppermint,
spearmint, tobacco, and soybeans (Special Local Need
Registration required in Mississippi and Texas only). Also
used to control cockroach (spot treatment only) in residential and industrial buildings and insect control in forests, and on ornamental plants and to target armyworms,
aphids, beetles, bollworms, borers, budworms, cankerworms, crickets, cutworms, fire ants, fleas, grasshoppers,
leafhoppers, loopers, mealybugs, mites, moths, roaches,
spiders, thirps, wasps, weevils, whiteflies, etc.
Trade name
ACECAP SYSTEMIC INSECTICIDE
IMPLANTS®; ACEFAL 75 PS®; ACEHERO®;
ACEPHATE 97 EG®; ACEPHATE 75SP®; ACEPHATE
PCO SP INSECTICIDE®; ACESUL®; ACE-TOX®;
ACHERO®; ACIFAT®; ADDRESS®; AIMTHENE®;
AMCOTHENE®; ASATAF®; ASIFY®; ATTACK®;
CHEVRON RE 12420®; CLEAN CROP ACEPHATE 80
DF SEED PROTECTORANT®; DREXEL ACEPHATE 75
WSP®; DREXEL ACEPHATE PCO SP INSECTICIDE®;
FATEL®; FORPHATE®, FORWARD®; KITRON®;
KORANDA® (acephate + fenvelerate); LANCER®;
ORCEPHATE®; ORTHENE®; ORTHENE 755®;
Acephate 3
ORTHO 12420®; ORTRAN®; ORTRIL®; PACE®;
PAYLOAD®; PILARTHENE®; PINPOINT®; PRECISE
ACEPHATE®; RACET®; RE 12420®; SAPHATE®; 75
SP®; VALENT ORTHENE TECHNICAL®; VEGFRU
TARGET®
Biological Activity
Anticholinesterase insecticide that produces cholinotoxicity. Displays weak inhibition of rat acetylcholinesterase (AChE) but potently inhibits cockroach AChE.
Mechanism of action
Broad-spectrum, contact and ingestion systemic action. Weak acetylcholinesterase (AChE) inhibitor.
Safety Profile
Poison by ingestion.
Moderately toxic by skin contact and
inhalation. Human mutation data reported.
When heated to decomposition it emits very
toxic fumes of NOx, POx, and SOx. See also
ESTERS.
Potential Exposure
Acephate is a general use contact and systemic insecticide. Banned in the EU for use as a biocide and agricultural insecticide. Used on green- and limabeans, Brussels sprouts, cauliflower, celery, cotton, cottonseed, cranberries, head lettuce, macadamia nuts, peanuts, bell-and nonbell peppers, peppermint, spearmint, tobacco, and soybeans (Special Local Need Registration required in Mississippi and Texas only). Also used to control cockroach (spot treatment only) in residential and industrial buildings and insect control in forests, and on ornamental plants and to target armyworms, aphids, beetles, bollworms, borers, budworms, cankerworms, crickets, cutworms, fire ants, fleas, grasshoppers, leafhoppers, loopers, mealybugs, mites, moths, roaches, spiders, thirps, wasps, weevils, whiteflies, etc. banned for use in the EU.
Carcinogenicity
Acephate showed no evidence of
carcinogenicity among rats given diets with 0, 5, 50, or
700 ppm (equivalent to about 0, 0.25, 2.5, and 35.0 mg/kg/
day, respectively) for 28 months .
Environmental Fate
Soil. In aerobic and anaerobic soils, methamidophos and carbon dioxide were identified
as the major soil metabolites (Hartley and Kidd, 1987). The estimated half-life in soil is
3 days (Wauchope, 1988)
Plant. Acephate is quickly absorbed, translocated and transformed in pine seedlings
(Werner, 1974) and cotton plants (Bull, 1979). The chemical was metabolized via cleavage
of the amide bond to form methamidophos (O,S-dimethyl phosphoramidothioat
Chemical/Physical. Emits toxic fumes of phosphorus, nitrogen and sulfur oxides when
heated to decomposition (Sax and Lewis, 1987)
Metabolic pathway
Acephate is a systemic insecticide with a very favourable mammalian
toxicity. The initial reaction of the biotransformation of acephate is by
hydrolysis to the active acetylcholinesterase inlubitor methamidophos. In
every case where the metabolism of acephate has been studied in biological
systems, the production of methamidophos has been demonstrated;
however, the amount of this presumed active metabolite varies
greatly from organism to organism. In mammals, which are relatively
insensitive to the insecticide, the primary route of stage I metabolism is
mainly degradative via O-demethylation to give des-O-methylacephate.
Further metabolism in mammals and birds leads to incorporation of the
molecule into proteins, carbohydrates and lipids as well as to excretion.
Conjugates have not been identified.
Shipping
UN2783 Organophosphorus pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials. UN3018 Organophosphorus pesticides, liquid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous material
Degradation
Acephate is relatively stable to hydrolysis, with DT
50s of 60 hours at pH 9
and 710 hours at pH 3 and 40 °C (PM).
Chukwudebe et al. (1984) studied the breakdown of acephate in 0.1M
Tris-HCl buffer at pH 7.2, 8.1 and 8.6 at 37 °C. The hydrolysis products
were analysed by GLC with FID for acephate and methamidophos and
TLC separation and GLC analysis for the other products. Authenticated
standards [methamidophos (2), des-O-methylacephate (3), des-S-methylacephate
(4) and O,S-dimethyl phosphorothioate (5)] were used to
calibrate the analysis. The major metabolite at all pH values was O,S-dimethyl
phosphorothioate (5). This reached a maximum concentration
of 40-55% in 1-3 days depending on pH. Its concentration then declined
as it was itself hydrolysed. The hydrolysis of acephate was strongly
biphasic, with hydrolysis becoming very slow after about 2 days. The
amounts of methamidophos (2) (3%) and des-S-methylacephate (4) (10%)
produced after 7 days were minor. Major and minor routes for the
hydrolysis of methamidophos are shown in Scheme 1.
Toxicity evaluation
Although methamidophos is highly toxic to mammals
(LD
50 mice = 27 mg/kg), the acetylation causes a dramatic
decrease in the mammalian toxicity; the acute oral
LD
50 values of acephate for mice and rats are 361 and
945 mg/kg, respectively. Inhalation LC50 is >15 mg/L air.
In 2 years of feeding trials, dogs showed depression of
cholinesterase at 100 mg/kg diet (5 mg/kg/d) (maximum
dose level). ADI is 0.03 mg/kg.
Incompatibilities
May react with strong oxidizers such as chlorates, peroxides, nitrates, etc. In the presence of strong reducing agents such as hydrides, organophosphates form highly toxic and flammable phosphine gas. Contact with oxidizers can cause the release of toxic oxides of phosphorus. Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water, and a salt that may be harmful. Incompatible with arsenic compounds(releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides (releasing heat, toxic and possibly flammable gases), thiosulfates and dithionites (releasing hydrogen sulfate and oxides of sulfur).
Waste Disposal
Alkaline hydrolysis or incineration. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Containers must be disposed of properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.
Pesticide Type
Insecticide
