The safest way to eliminate the horehound in your pasture is to dig it out or burn it out. You can use herbicides that have 2,4-D and/or Dicamba also. These are herbicides and have low toxicity to bees. Your own care of application of these herbicides will lower the risk to bees even more. Do not spray when the horehound is in bloom as bees may be visiting the flowers. Spray in late afternoon or the evening as bees will not visit flowers that have started to curl. Spot spray the horehound. Use of a cone over the spray tip will help direct the spray to the specific weed. Do not spray when it is windy or temperatures will be over about 80 degrees for the next couple of days; this is to reduce drift to other plants that may be in bloom and that you do not want to damage. Always read and follow directions on the product label; it may have suggestions for bee safety also.

Horehound is pretty easy to control by digging so this is a good option if you don't have too much of it. If you have a lot, maybe a barbeque is in order...work first of course.