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<br />. Chlorpyrifos-impregnated ear tags are under development to control horn <br />flies (Haematobia irritans) in U.S. cattle (Byford et al. 1986). Cattle <br />fitted with ear tags (0.96 g chlorpyrifos per tagj365 kg animal, or about 2.6 <br />mg chlorpyrifosjkg BW) had s~ightly elevated tissue residues (0.13 mg/kg fat) <br />after 12 weeks, but residues were well within current acceptable tolerance <br />levels of 2.0 mg chlorpyrifos/kg fresh weight cattle fat, meat, or meat <br />by-products (Byford et al. 1986). In dogs . (Canis familiaris), <br />chlorpyrifos-impregnated collars provided effective control of adult fleas <br />(Ctenocephalides spp.) for up to 11 months, with no significant adverse <br />reactions regardless of canine coat length, size, or age (Higgins and Jarvis <br />1986). <br /> <br />16 <br />