malathion, broad-spectrum organophosphate insecticide and acaricide (used to kill ticks and mites). Considerably less toxic to humans than parathion, malathion is suited for the control of household and garden insects and is important in the control of mosquitoes, boll weevils, fruit flies, and lice.
Malathion is a colourless to yellow-brown liquid with a characteristic unpleasant odour. It is generally prepared by combining O,O-dimethyl phosphorodithioate with diethyl maleate. It is soluble in most organic solvents except paraffin hydrocarbons and is practically insoluble in water. Malathion is readily decomposed by alkalies. The chemical works by binding to the enzyme acetylcholinesterase (AChE) at nerve endings, thus disrupting the neurotransmitter acetylcholine (ACh) and ultimately causing death.
Malathion is highly toxic to bees and other beneficial insects, aquatic invertebrates, and some species of fish, notably bluegill and largemouth bass. It is of moderate toxicity to birds.