Diflubenzuron (CAS No. 35367-38-5), besides its use in agriculture, horticulture and forestry against larvae of Lepidoptera, Coleoptera, Diptera, Hymenoptera, and in public health against larvae of mosquitoes, is used as a veterinary drug for the treatment of sea lice (Lepeophtheirus salmonis Kr øyer and Caligus rogercresseyi Boxshall and Bravo, 2000) infestations in Atlantic salmon (Salmo salar L.). Diflubenzuron acts by interference with the synthesis of chitin. Demand for chitin synthesis is greatest at the moult between growth stages and hence parasites are killed due to disruption of the moulting process.