Mercaptodimethur

Description

Methiocarb was originally developed by Bayer as an insecticide. The bird-repellent properties of the compound were quickly recognized, however, and a number of applications for bird damage management followed (42).
Methiocarb is a secondary repellent, and repellency occurs through aversive conditioning, by which birds that feed on treated food become sick and associate either the food or characteristics of the food with the discomfort (21). As a result, affected birds learn to avoid that food item. Often the avoidance response is locationdependent. For example, common ravens (Corvus corax) that learn not to eat eggs at one site will still feed on eggs at a different location (43).

Chemical properties

Methiocarb is a colorless crystalline powder.

The Uses of Mercaptodimethur

Insecticide; molluscicide; bird repellent.

The Uses of Mercaptodimethur

Insecticide, acaricide and bird repellent.

The Uses of Mercaptodimethur

Methiocarb is an insecticide, molluscicide and acaricide with contact and stomach action. It is used to control slugs, snails and insects in a wide range of crops. Soil insects are controlled. Methiocarb is also used as a seed-treatment and bird repellent.

Definition

ChEBI: A carbamate ester obtained by the formal condensation of the phenolic group of 3,5-dimethyl-4-(methylsulfanyl)phenol with the carboxy group of methylcarbamic acid.

General Description

White crystalline powder with a mild odor. Used as an insecticide and immobilizing agent for birds, acaricide and molluscicide.

Reactivity Profile

Mercaptodimethur is a carbamate ester. Carbamates are chemically similar to, but more reactive than amides. Like amides they form polymers such as polyurethane resins. Carbamates are incompatible with strong acids and bases, and especially incompatible with strong reducing agents such as hydrides. Flammable gaseous hydrogen is produced by the combination of active metals or nitrides with carbamates. Strongly oxidizing acids, peroxides, and hydroperoxides are incompatible with carbamates.

Health Hazard

As a carbamate insecticide, Mercaptodimethur is a reversible cholinesterase inhibitor and acts on the nervous system. It is classified as very toxic, and the probable oral lethal dose for humans is 50-500 mg/kg or between 1 teaspoon and 1 ounce for a 150 lb. adult.

Health Hazard

Highly toxic cholinesterase inhibitor; exhibitsacute, delayed and chronic effects; routesof entry — ingestion, skin absorption andinhalation of vapors; reversible action ofshort duration; toxic symptoms includesalivation, lacrimation, bradycardia, blurredvision, labored breathing, headache, muscle twitching, tremor, and slight paralysis;gastrointestinal effects include nausea, vomiting, abdominal pain, and diarrhea; severepoisoning may lead to convulsions and coma;oral intake of probably 5–10 g may be fatalto adult humans.
LD50 oral (rat): 15–20 mg/kg
LD50 oral (guinea pig): 40 mg/kg
LD50 skin (rat): 350 mg/kg
LD50 skin (wild bird): 100 mg/kg.

Fire Hazard

When heated to decomposition, Mercaptodimethur emits very toxic fumes of nitrogen and sulfur oxides.

Agricultural Uses

Acaricide, Molluscicide, Insecticide: Used to control slugs and snails, soil insects and spider mites in pome fruit, stone fruit, hops, strawberries, potatoes, beets, maize, vegetables and ornamentals. Also used as seed treatment to control fruit flies on maize and bird repellant on berries and cherries. Methiocarb producers deleted all food uses from their product labels between 1989-92. It is A U.S. EPA restricted Use Pesticide (RUP) except for residential application.

Trade name

AI3-25726®; ALCO SLUB”M[C]; B 37344®; BAY 5024®; BAY 9026®; BAY 37344®; BAYER 37344®; DCR 736®; DRAZA®; DRAZA G MICROPELLETS®; H 321®; MESUROL®; METHIOCARBE®; OMS- 93®; PBI SLUG GARD®; PROVADA®; SD 9228®; SLUG-GETA®[C]

Contact allergens

Methiocarb is an insecticide or molluscicide with a cholinesterase inhibiting effect. A case of contact dermatitis was reported in a carnation grower.

Pharmacology

Methiocarb is a carbamate, and its mode of action is via the inhibition of acetylcholinesterase at synapses in the nervous system. Unlike many cholinesterase-inhibiting compounds, however, the effects of methiocarb are rapidly reversible, and the animal experiences only transitory disruption.

Safety Profile

Poison by ingestion, skin contact, and intraperitoneal routes. Used as an insecticide, molluscicide, and bird repellent. When heated to decomposition it emits very toxic fumes of NOx and SOx. See also ESTERS and CARBAMATES.

Potential Exposure

A potential danger to those involved in the manufacture, formulation, and application of this nonsystemic acaricide and insecticide.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Speed in removing material from skin is of extreme importance. Shampoo hair promptly if contaminated. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. Keep victim quiet and maintain normal body temperature. Effects may be delayed; keep victim under observation.

Environmental Fate

Soil. Methiocarb was oxidized, probably by singlet oxygen, to the corresponding sulfoxide and trace amounts (<5% yield) of sulfone when sorbed on soil and exposed to sunlight. The photosensitized oxidation was faster in soils containing the lowest organic carbon content (Gohre and Miller, 1986).
Plant. On and/or in bean plants, the methylthio group is rapidly oxidized to the sulfoxide and sulfone (Abdel-Wahab et al., 1966) followed by hydrolysis yielding the corresponding thiophenol, methylsulfoxide phenol and methylsulphonyl phenol (Har
Photolytic. When methiocarb in ethanol was irradiated by UV light, only a few unidentified cholinesterase inhibitors were formed (Crosby et al., 1965).
Chemical/Physical. Emits toxic fumes of nitrogen and sulfur oxides when heated to decomposition (Sax and Lewis, 1987).

Metabolic pathway

Methiocarb is oxidised to a sulfoxide and a sulfone in biological media. The resulting two carbamate esters and the parent compound are hydrolysed in soils and plants to the corresponding phenols. Hydroxylation of the N-methyl group on the carbamate function occurs in mammalian preparations in vitro.

storage

Color Code—Blue: Health Hazard/Poison: Store in a secure poison location. Prior to working with this chemical you should be trained on its proper handling and storage. Store in tightly closed containers in a cool, wellventilated area

Shipping

UN2757 Carbamate pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials. UN2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Degradation

Methiocarb is unstable in alkaline solution. Its DT₅₀ values at pH 4,7 and 9 (22 °C) are >1 year, 35 days and 6 hours, respectively. Photodegradation (DT₅₀ 6-16 days) contributes to the loss of methiocarb from the environment (PM).
River water containing methiocarb was stored in sunlight or artificial light. Samples were taken and analysed by TLC. Methiocarb was rapidly hydrolysed (half-life 3 days) to the phenol (2) which itself degraded (Eichelberger and Lichtenberg, 1971).

Waste Disposal

In accordance with 40CFR 165 recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Remove material with contaminated soil and place in impervious containers. May be incinerated in a pesticide incinerator at the specified temperature/dwell-time combination. Any liquids, sludges, or solid residues generated should be disposed of in accordance with all applicable federal, state, and local pollution control requirements. If appropriate incineration facilities are not available, material may be buried in a chemical waste landfill. May be amenable to biological treatment at a municipal sewage treatment plant. (Sax/DPIMR).