Methomyl

Methomyl is a carbamate insecticide used on a wide range of crops, including fruits, vegetables, and field crops. It is formulated in various product forms, such as emulsifiable concentrates, granules, and wettable powders, and is marketed under several brand names, including Lannate. It is employed for control of caterpillars, beetles, aphids, and whiteflies, among other pests.

Methomyl acts as an inhibitor of acetylcholinesterase, an enzyme essential for terminating nerve signal transmission. By blocking this enzyme, it causes accumulation of acetylcholine at synapses and neuromuscular junctions, leading to rapid overstimulation of the nervous system in insects and, at sufficiently high exposures, in mammals and birds. The onset of effects is typically rapid after exposure.

Toxicology and safety: Methomyl is highly toxic to humans and many non-target organisms. Exposure can produce cholinergic symptoms such as salivation, lacrimation, urination, defecation, tremors, muscle weakness, and, in severe cases, respiratory failure. It poses notable risks to bees and aquatic life, and therefore careful handling and adherence to label directions are essential. Applications should minimize drift and avoidance of non-target exposure.

Environmental fate and regulation: Methomyl degrades in soil and water through hydrolysis and microbial action, and is generally less persistent than many organophosphates, though residues can occur with repeated use. It can contaminate surface water via drift or runoff if not properly managed. Regulatory status varies by country; many jurisdictions classify methomyl as a restricted-use pesticide requiring trained applicators, protective equipment, and adherence to strict labeling, application, and disposal guidelines.