A unique, slow-release ear tag for cattle that is the first ever tag to contain abamectin (avermectins B1a and B1b), a highly active macrocyclic lactone. The patent-pending formulation contains a high loading of piperonyl butoxide, which synergizes the abamectin for maximum pesticidal action. This tag is particularly effective against horn flies, including strains resistant to synthetic pyrethroid and organophosphate insecticides. It is also effective against ear ticks, American Dog Ticks, Cattle Fever Ticks (Boophilus species) and Lone Star Ticks. The tag has a net weight of 9 grams and a metallic gold color.