Methiocarb is a carbamate pesticide (an acetylcholinesterase inhibitor) which is used as an insecticide,[1][2] bird repellent,[3] acaricide[2] and molluscicide[2] since the 1960s.

Methiocarb has contact and stomach action on mites and neurotoxic effects on molluscs.

Due to its toxicity, methiocarb approval as a plant protection product has been withdrawn by the EU effective 2020.

[6] The xylenol (1) will act as the nucleophile in this reaction attacking the partially positively charged carbon in the isocyanate (2).

[1] The product of the cleavage of the carbamate group of methiocarb is methylcarbamic acid which is bound to cholinesterase after the reaction.

[citation needed] In addition to its cholinergic effects, methiocarb has been found to be an endocrine disruptor, acting as an estrogen, antiandrogen, and aromatase inhibitor.

For absorption through the skin the NOAEL is set to 150 mg/kg per day for rabbits, based on the reduction of food consumption.

[8] When methiocarb is fed to rats at a dose of 50 ppm, it gives a reduction of brain cholinesterase by 14% and 5% in males and females respectively.

When methiocarb is administered as an aerosol to rats, the highest concentration (96 mg/m3 in solvent) showed signs of involuntary muscle contraction (tremors).

The brain acetylcholine esterase is reduced in comparison to the solvent controls, to 61% and 74% for males and females respectively.

The NOAEL was determined to be 6 mg/m3 based on the reduction of brain acetylcholine esterase activity.

About 8 hours after IP injection of [14C]methiocarb more than 20 is present in the kidneys, 14 in the lungs, 14 in the heart, 6 in the body fat and 26 in the red blood cells.

30 Minutes after treatment gave, for all tissues except bodyfat, much higher values indicating that elimination takes place shortly after injection.

Also, an increase in all tissues except the red blood cells has been observed between 2 and 4 hours after injection.

[8][11] In rabbits methiocarb was applied to the skin to a group of ten at doses of 0, 60, 150 or 375 mg/kg bw per day for 6 h/day.

Cholinesterase activity was reduced in males with a high dose at 14 and 21 days of treatment.

Environmental fate in water and soil has been determined from the metabolites formed by anaerobic as well as aerobic degradation, photolysis, adsorption and leaching of methiocarb.

In a research with E. vermiculata, methiocarb showed to be the most effective as topical applicant (although DMSO was used as a solvent).

[21] In another study with quelea, it was investigated if methiocarb had an adverse effect on the food choice.

It showed that when quelea ate seeds with methiocarb, the next time they would choose some other food.

In the first field trial, snail pellets of methiocarb were spread across the land and killed almost 23% of the initial mice population in one night, but the population did not decrease (probably because of reinvasion of the neighbouring land).

[24] †Semiquantitative analysis was performed by the approximation of similar extinction coefficients of mercaptodimethur and its metabolite descarbamoylmercaptodimethur at wavelength 200 nm.