Editor's note: The following information is from the University of Minnesota, but is applicable to many sections of the country. Contact you local county extension service or university agriculture department for information in your state.
Question: Is there an insecticide that can be used in a horse pasture to control deer ticks? The tick pressure is really high this year. Any other ideas for controlling ticks?
Response: There are two kinds of ticks that are common on Minnesota livestock; American dog ticks (i.e., wood ticks) and black‐legged ticks (i.e., deer ticks). Deer ticks seem to be expanding their territory and are spreading west in the state. Only deer ticks spread the Lyme disease bacterium. It would be worth knowing what kind(s) of ticks are feeding on your horses.
For both kinds of ticks, they are most abundant in shrubby ground with deciduous tree over‐story, mainly because the smallest forms (larvae) feed on small rodents, and small rodents need the cover and tree seeds for food. Therefore, habitat management can be used to keep tick populations low.
Horses on pasture can be protected by fencing to keep the horses from getting into the woods, and by mowing pasture perimeters to keep mouse and tick populations low around pasture margins. I don't think much would be accomplished by spraying pastures in most situations, but if it were done, a water‐base spray of permethrin formulated for "mosquito" or "premise fly" control should be safe for mammals, including horses.
For more information from the University of Minnesota horse extension please visit their website.