Best Feed Through Fly Control For Horses – 2026 Reviews

This is the most critical distinction. Insect Growth Regulators (IGRs) like diflubenzuron (in SimpliFly) or novaluron (in MultiFly) are larvicides. They pass through the horse, work in the manure, and prevent fly larvae from developing into adults. They control the population at its source and are incredibly effective but require time to break the cycle.

Natural repellents, often garlic or yeast-based like Bug Clear, aim to make the horse’s system less appealing to biting insects. They may help repel adult flies but don’t stop breeding. Choose an IGR for proven population control; choose a natural repellent for a gentle, supplementary approach.

If a product is labeled as an EPA-registered pesticide (like Farnam SimpliFly), that’s a major signal of trust. It means the manufacturer had to provide substantial scientific data to the Environmental Protection Agency proving both safety and efficacy. Products without this registration are classified as supplements, and their performance claims aren’t held to the same rigorous standard. For guaranteed results, an EPA-approved product is your safest bet.

The best fly control in the world is useless if your horse won’t eat it. Look for terms like ‘highly palatable,’ ‘flavorless pellets,’ or ‘mixed with sweet feed.’ Pelleted forms often blend into grain better than powders. If you have a notoriously picky eater, you might even consider doing a small test batch before committing to a giant bucket. Consistency is key with feed-throughs, so acceptance is non-negotiable.

Feed-through fly control is preventative, not reactive. You must start feeding before flies become a problem-ideally in early spring-and continue daily throughout the fly season. It can take 2 to 6 weeks to see a significant reduction, as the product works on the next generation of flies. Don’t give up if you don’t see instant results; you’re playing the long game.

For the best results, think of a feed-through as the cornerstone of an Integrated Pest Management (IPM) plan. It drastically reduces the breeding population, but you’ll still need other tools like fly masks, sprays, traps, and good manure management to handle adult flies that migrate in from elsewhere. This multi-pronged approach is what truly brings peace to your barn.

Calculate the cost per day, not just the sticker price. A large bucket like Farnam Equitrol II has a high upfront cost but provides a full season for one horse. For a multi-horse barn, buying in larger quantities (like the 10lb SimpliFly or MultiFly) is almost always more economical than multiple small containers.

You need patience! Since these products work by interrupting the fly life cycle in the manure, they don’t kill existing adult flies. It typically takes 4 to 6 weeks of consistent daily feeding to see a noticeable decline in the overall fly population around your barn. The key is to start early, well before peak fly season, so you’re stopping the next generation before it ever takes flight.

The products on this list, including the EPA-approved IGRs, are formulated to be safe for horses of all ages and life stages when used as directed. However, you must follow the labeled dosage instructions based on your horse’s weight. Always check with your veterinarian if your horse is pregnant, nursing, has a known health condition, or is on other medications. Crucially, note that these products are NOT for use in horses intended for slaughter.

You will likely still need supplemental control. A feed-through is brilliantly effective at reducing the breeding population on your property, but it won’t affect adult flies that fly in from neighboring fields or other breeding sites (like compost piles). A combination approach-using your feed-through alongside fly sprays, masks, and traps-is the gold standard for keeping your horses comfortable and stress-free all season long.

Both contain the same active ingredient (diflubenzuron) and work identically. The primary difference is the form and package size. SimpliFly comes in pellet form in 3.75lb and 10lb buckets. Equitrol II is formulated as a feed additive and comes in a much larger 20lb bucket designed as a full-season supply for one horse. Choose based on your preferred volume and how many horses you’re treating.

For severe fly infestations, a natural repellent like a garlic-based supplement is usually not sufficient on its own. These products can be helpful as part of a holistic plan or for mild pressure, but their effectiveness is more variable and less proven than EPA-approved Insect Growth Regulators (IGRs). If you’re dealing with a major fly problem, an IGR-based feed-through will give you a much more reliable and significant reduction.