ClariFly Larvicide is a feed supplement that prevents adult house flies, stable flies, face flies, and horn flies from developing in and emerging from the manure of treated cattle. When mixed into cattle feed, ClariFly passes through the digestive system and into the manure. It can be blended into all calf feeds, lactating feeds and milk replacers. Because the active ingredient is considered a low risk to human health by the E.P.A. there is no meat or milk withholding. Begin feeding ClariFly early in the spring before flies begin to appear, and continue feeding though the summer and into the fall until cold weather reduces or ends fly activity.