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Lice are wingless ectoparasitic insects that can irritate and injure their hosts and transmit pathogens. Horses and ponies can be infested with a chewing louse, Bovicola equi (Denny) (Phthiraptera: Trichodectidae), that irritates the animals, creates skin lesions, causes hair loss, and generally reduces animal fitness (Mencke et al., 2005, Larsen et al. 2005). In addition to irritating their hosts, some lice of livestock have been associated with rickettsial pathogens (Reeves et al. 2006).
Chemical control of lice has been accomplished with a wide range of systemic and topical insecticides including pyrethroids, organochlorines, organophosphates, carbamates, macrocyclic lactones, insect growth regulators, and botanical derivatives (Losson 1990). Many pesticides used for louse control are no longer available. Benzoylphenylureas such as diflubenzuron (Dimilin) and triflumuron are chitin synthesis inhibitors. Triflumuron was recently reported to control B. equi in Australia when applied as a pour-on (Lowden et al. 2007) and Dimilin has been shown to be effective in controlling Bovicola bovis L. on cattle (Campbell et al. 2001). We report on the insecticidal activity of Clean-UpTM (KMG Chemicals, Houston, TX), a pour-on insecticide containing 5% Dimilin mixed with...