Methidathion is a non-systemic organophosphate insecticide and acaricide applied against scale insects, mealybugs, whiteflies, and spider mites on citrus, olives, grapes, and other fruit crops. It acts on contact and through vapor by inhibiting cholinesterase in the nervous systems of target pests. Its high acute toxicity to humans, birds, and aquatic life has led to bans or severe restrictions in many regions, and where any use remains, maximum residue limits and pre-harvest intervals apply. Monitoring programs test fruit shipments for methidathion residues with multi-residue methods, and importing countries reject consignments that exceed their tolerances. Applicators historically required protective equipment and restricted-entry intervals.