Get a jump start on fly control. Start your horse on SimpliFly feed-thru fly control with LarvaStop early in the spring and continue throughout the summer until cold weather restricts fly activity. SimpliFly is a feed supplement for horses that prevents stable and house flies from living in your horse's manure. This supplement concludes the life cycle of fly larvae by impeding their exoskeleton's formation, ultimately killing any potential new larvae. SimpliFly is considered a reduced risk pesticide, making it safe to use for pest management.