I didn't want to use anything too terribly toxic, because it's outside and the sheep or goats might get to it. We've got a bottle of poison specifically designed for use on animals. It contains permethren, an artificial pyrethroid, which are generally harmless to mammals (except cats). I noticed the box brags that the spray has a baby-powder scent. Then I noticed in the warnings that you're not supposed to inhale the vapors.
If you're not supposed to be smelling it, why make it a pleasant baby powder scent?