SimpliFly Feed Thru Fly Control helps reduce house and stable fly populations by preventing fly larvae from developing in horse manure. When fed daily, the active ingredient diflubenzuron passes through the horse unabsorbed and is deposited in the manure, stopping flies from breeding at the source. This highly palatable formula mixes easily with your horse's daily feed and is made without organophosphates. For best results, begin feeding in early spring before fly season, though it can be started at any time during the season. As part of a complete fly management program, SimpliFly Feed Thru Fly Control helps create a cleaner, more comfortable stable environment.