Milkweed Aphids

I was walking by my swamp milkweed plants the other day and noticed them covered in something yellow.  Upon closer inspection I saw the yellow "dots" moving, and realized that I had milkweed aphids.  

Rather than use chemicals to get rid of them, I prefer to spray them with the water hose.  It knocks them off the plant, but keeps any monarch eggs safe.  I have also used a cotton swab to remove them from the plants.  If the aphids keep returning you can also take a cotton swab dipped in rubbing alcohol to them.  It is tedious but kills them on contact.