Fly Control for Show Livestock: Where Flies Breed and What Is Safe on Your Animals

Most fly control for show cattle, sheep, goats and pigs happens off the animal. Find the wet spots where flies breed and clean them out every week. As soon as you see the first flies in the spring, treat the barn surfaces where they rest with a premise product. If you put anything on the animal himself, use the fly spray your veterinarian recommends.

In the skin problems article, I promised you a full piece on flies and said you could hold me to it. Here it is, and it applies to every species in your barn.

Know which fly you are fighting

House flies are the ones on everything. They do not bite. Their mouthparts sponge up food rather than pierce skin. They breed in manure and spilled feed, and they carry filth from one place to the next.

Stable flies look a lot like house flies, but they bite. They have a piercing mouthpart and feed on blood, and they go after the legs hardest. On a pig, their bites show up as separate, countable red spots with normal skin between them, the bite picture that gets called mange on Facebook. Stable flies breed in wet, spoiled feed, hay and bedding, especially where it is mixed with manure.

Mosquitoes breed in standing water and bite mostly at night. A barn light left on draws them right to your animals.

On cattle, sheep and goats, watch for a few more:

• Horn flies sit on the back and sides of cattle, mostly cattle out on pasture, and bite all day.
• Face flies cluster around the eyes and nose of cattle. They do not bite, but they feed on tears and can spread pinkeye.
• Blowflies lay eggs in wet, dirty wool or hair and in wounds, and the maggots feed on the animal. In sheep and goats that is fly strike. It needs attention the day you find it, so call your vet.

New World screwworm is the one to know about right now, in every species. It is a fly that lays its eggs in open wounds, even small ones like a fresh ear tag hole, a scrape or a newborn’s navel, and its maggots eat living flesh. It was confirmed in the United States in June 2026, and as of October cases have been confirmed in livestock in Texas and New Mexico. It is a reportable disease. Check your animals for wounds at every feeding, and if you ever find maggots in a wound, call your veterinarian that day. More in our screwworm guide for show families.

If you live where screwworm has been found, or you haul from there, do more:

• Know the map. States draw quarantine zones around confirmed cases and change them often. In Texas, animals cannot leave an infested zone without the Texas Animal Health Commission’s OK, which means an inspection and a movement certificate before you load. Check your state animal health agency before every trip.
• Check the show’s rules early. States and shows can set their own screwworm entry requirements, and those can change between entry day and show day.
• Make fewer wounds, and protect the ones you have. Talk with your vet before tagging, castrating, dehorning or docking, and about protecting any wound you cannot avoid. Then look at every wound at every feeding.

The life cycle, and why spraying the flies you see is not enough

Every fly goes through four stages: egg, maggot, pupa and adult. A female lays her eggs in wet organic material, the maggots grow there, and the adult crawls out ready to start over. In summer, a house fly goes from egg to adult in about two weeks, and a stable fly in about three.

The flies you see on the walls are only the adults. Most of the population is down in the wet spots as eggs, maggots and pupae. Spraying the adults buys you a few days. Cleaning out the places they breed every week, before the maggots finish, is what actually brings the numbers down.

Where flies breed on your place

If it is wet and has organic material in it, flies can breed in it. Around a show barn, that usually means:

• under fences and gates, where bedding and manure get pushed and stay damp;
• the corners of the pen;
• around and under the feeder or bunk, where spilled feed gets wet;
• under hay feeders, where wasted hay builds up and stays wet;
• around the waterer, where drips keep the ground wet;
• the wash rack drain, and wherever the runoff ends up;
• the manure pile, especially if it sits close to the barn;
• old bedding, hay or straw that got wet, and piles of grass clippings.

For mosquitoes, look for anything that holds water for a week: buckets, old tires, a clogged gutter, a low spot in the yard.

Make it a weekly fly walk. Once a week, walk the place with that list. Scrape out anything wet and dirty, let the spot dry, and haul the material away from the barn.

Premise control done properly

Premise products go on the building, where flies land and rest between meals. Two I use are Agita (Elanco, thiamethoxam) and PT Alpine (BASF, dinotefuran). Start them as soon as you start seeing flies in the spring. Put them on walls, ledges, windowsills and posts, the places flies sit.

Agita and PT Alpine go on surfaces. They do not go on your animals. Not on their skin, not in a pen where they can lick it, and not mixed into anything that touches them. Follow the label for how much to use and how often to put it back out. I am not publishing rates, because the label is the instruction and mine is not.

Turn the barn lights off at night. A light left on brings the mosquitoes to your animals.

There are other tools, such as fly traps, sticky ribbons, bait stations and fly predators (tiny wasps that kill fly pupae). Anything with bait or insecticide in it goes where your animals cannot reach it.

Fans are not fly control. A fan keeps an animal cool in the summer, but it does not count as fly or mosquito control, so do not build your fly plan around one.

What is safe on your animals

This is where families get in trouble. Many of the fly sprays sitting in a barn are labeled for horses only, and a product labeled for one species is not automatically safe for another. Your show animal is a food animal, with a withdrawal time attached to anything you put on him.

Use the fly spray your veterinarian recommends. I am not naming one here, because the right one depends on your species, your barn and your show calendar, and that is a conversation with your vet. Check your show’s rules too.

Your fly plan in one list

• When the first flies show up in spring: Agita or PT Alpine on the barn surfaces.
• Every week: the fly walk. Clean out every wet spot with organic material in it.
• Every night: barn lights off.
• On the animal: the fly spray your veterinarian recommends.
• Sheep and goats: check for fly strike in dirty wool or hair and in any wound.
• Spots on a pig’s skin: separate, countable spots are bites. The skin problems article walks you through telling bites from dermatitis and mange.

Questions show families ask about flies

What is the best way to control flies in a show barn?

Start with where they breed. Once a week, clean out every wet spot that has organic material in it, like under fences, in pen corners, under hay feeders and around feeders and waterers. As soon as flies show up in spring, put a premise product on the barn surfaces where they rest, and turn the lights off at night. On the animal, use the fly spray your veterinarian recommends.

Which flies bite show animals?

Stable flies bite and feed on blood, mostly on the legs. Horn flies bite cattle, mostly cattle on pasture. Mosquitoes bite too, mostly at night. House flies and face flies do not bite, but face flies can spread pinkeye in cattle.

Can I use horse fly spray on my show animal?

Ask your veterinarian first. Many barn fly sprays are labeled for horses only, and your show animal is a food animal with a withdrawal time on anything you put on him. Use the fly spray your veterinarian recommends.

Where do flies breed in a show barn?

Anywhere wet that has organic material in it: under fences and gates, in pen corners, in spilled feed around the feeder or bunk, under hay feeders, around the waterer, at the wash rack drain, in wet bedding and in the manure pile. Mosquitoes breed in standing water.

Are Agita and PT Alpine safe to use around livestock?

They are premise products for the building. They go on walls, ledges, windowsills and posts where flies rest, never on the animals and never where they can reach or lick them. Follow the label for how much and how often.

What is New World screwworm?

A fly that lays its eggs in open wounds on any warm-blooded animal, and its maggots eat living flesh. It was confirmed in the United States in June 2026, with cases in livestock in Texas and New Mexico as of October. It is a reportable disease. If you find maggots in a wound, call your veterinarian that day. If you live in or haul from an area where it has been found, check your state animal health agency’s quarantine map and your show’s entry rules before you move animals.

Do fans keep flies off show animals?

No. A fan helps keep an animal cool, but it is not fly or mosquito control. Breeding-site cleanup and premise products are what bring the fly numbers down.