Cotton leafworm (Alabama argillacea H.) was the primary pest of cotton (Gossypium hirsutum L.) in the USA during the 1800s. It was controlled by non-chemical means, such as hand-crushing the caterpillars, keeping large poultry yards, and using fires and lamps to attract and kill the adult moths. In 1873, USDA scientists recommended Paris green, a copper acetoarsenite compound, for control of cotton worm. This product and London purple, an arsenic-containing aniline dye introduced in 1878, successfully controlled cotton worm but not boll weevil (Anthonomus grandis grandis B.), which had a different feeding habit. The standardized application method in 1890 was dusting from two insecticide-containing bags affixed to the opposing ends of a pole held transversally across a trotting horse or mule. Changes in application equipment, coupled with the shift to calcium arsenate insecticide, allowed successful control of boll weevil from about 1919 until DDT was introduced following World War II. In 1945, 27 to 32 million kilograms of calcium arsenate were used by US farmers to control boll weevil. Reduced productivity of cotton soils containing arsenical insecticide residues was first reported in the 1930s, with the relative severity varying with soil clay content, pH, phosphorus status, and iron content. Experiments suggested that iron sulfate amendment could reduce phytotoxicity. It was generally concluded that fixation of arsenic by heavy soils and leaching of arsenic in sandy soils would prevent cropping problems caused by continued use of calcium arsenate. Arsenic was reintroduced to cotton production when arsenic acid was adopted in the 1950s as a chemical desiccant to aid harvest. Consequent elevated arsenic concentrations in cotton gin wastes and cotton bales led to localized arsenic contamination in solid and processing water waste disposal sites. All registrations for the use of inorganic arsenical compounds as desiccants were voluntarily cancelled in 1993.