Fly control in livestock facilities: treating the breeding surface instead of spraying adults

Adult flies are the last stage of a cycle that runs in the manure, not in the air. A house fly goes from egg to adult in about a week, so spraying adults never catches up. Fly control works when you remove the moist breeding surface the larvae need.

Why does spraying adult flies stop working by August?

Most fly programs start in May with a spray, a few strips, and a bait station. By the second week of July the flies are back. By August the spray does nothing at all. Producers usually blame the chemical. The chemical is only part of it.

Two things are working against a spray-only program.

The first is arithmetic. The flies you can see are the smallest part of the population on your place. For every adult on the wall, there are eggs, larvae, and pupae in the manure surface that no adulticide touches. Kill 90 percent of the adults on Monday and the pupae that were already in the crust hatch out Thursday. You have not reduced the population. You have thinned one age class of it.

The second is resistance. House flies run a complete generation in about a week in summer heat. That means you can put twenty or more generations through a single fly season. Any population turning over that fast, under repeated exposure to the same active ingredient, will select for survivors quickly. House fly resistance to pyrethroids is well documented across the country. The spray did not get weaker. The flies got harder.

You cannot outspray a reproduction rate. You can take away the place where reproduction happens.

What does a fly's life cycle actually look like?

Two species matter most in confinement and around cattle barns. They breed in different material and they hurt you in different ways.

The stable fly is the one that costs cattle money. It is a blood feeder with a painful bite, and it works the lower legs. Cattle respond by bunching, stamping, tail switching, and standing in ponds or shade instead of eating. A 2012 study in the Journal of Medical Entomology put annual stable fly losses to the U.S. cattle industry at about $2.2 billion, and the mechanism is not mysterious: animals that spend the afternoon fighting flies are not spending it at the bunk.

The house fly is the one that costs you your reputation. It does not bite. It reproduces faster than anything else on the place, moves freely between rooms, carries bacteria mechanically on its body and feet, and it will travel a mile or more from where it hatched. That last part is why fly problems become neighbor problems, and neighbor problems become county board problems.

Why is a crust close to a perfect fly nursery?

House fly larvae are particular about moisture. Too wet and they drown. Liquid manure with an open surface does not produce many flies, because larvae cannot survive submerged. Too dry and they desiccate. Dry lot manure that has baked for a week is not much of a nursery either.

What they want is the middle: moist, warm, loose, organic, and above the waterline. A pit crust hits every one of those.

A crust forms when the bacterial population that digests cellulose fiber cannot keep up with what is coming into the pit. Undigested feed fiber and bedding float, mat together, and set up as a mat across the top of the pit. That mat holds moisture from below and dries slightly on top. It insulates itself, so it stays warm. It is loose enough for a larva to move through. And it sits on top of the liquid instead of in it.

You have built, without meaning to, several thousand square feet of ideal fly habitat, with a heat source under it and a moisture source under it, refreshed daily. There is more on how the mat forms and why it hardens in what causes manure crusting.

The same logic applies to the other wet organic material on the place. Spilled feed under a bunk, wet hay along a fence line, bedding pack edges, and the ring of wet material around a lagoon berm are all stable fly ground. Stable flies in particular are far more interested in wet spilled feed mixed with manure than in the manure itself.

What is a fly problem actually costing you?

Put numbers on it before you decide what to spend.

• Intake and gain. Bunched cattle are not eating cattle. Stable fly pressure above threshold pulls animals off the bunk during the hottest, highest-pressure part of the day.
• Labor. Somebody is walking the barn with a sprayer instead of doing something else.
• Chemical. Repeat applications on a resistant population are money spent for a two-day effect.
• Pathogen movement. House flies move bacteria mechanically between rooms and between sites. They do not respect your barn-to-barn biosecurity line.
• Neighbors. Flies travel. A complaint call is cheap. A nuisance action is not.
• Help. Nobody wants to work in the barn where the flies are bad, and that shows up in your labor market before it shows up anywhere else.

What does an integrated fly program look like?

The order matters. Sanitation first, then physical control, then chemistry as a supplement, not as the program.

1. Remove the breeding surface. This is the only step that changes the population instead of the count. In a pit or lagoon barn, that means breaking up the floating fiber mat and keeping solids in suspension so the surface is liquid instead of a mat. LTC-E is the product made for high-fiber manure and crusting, and the approach is described on the how PitCharger works page: help break down the fibrous material so the crust weakens and moves back into the manure system.

2. Clean up the wet feed. Under the bunk, around the feeders, along the alley. Stable flies live there. A Feed Digester application handles the material that a scraper will not.

3. Dry what you can dry. Fix the leaking waterer. Fix the drainage that keeps that corner wet. Every square foot you dry out is habitat removed.

4. Then use traps, baits, and targeted residual sprays on the adults that are left, and rotate active ingredients so you are not selecting for resistance with one chemistry all season.

5. Count. Spot cards or a walk-through count on a set day each week. If you are not counting, you cannot tell whether anything you did worked.

Where does pit treatment fit, and how long does it take?

The timeline is different from a spray program. Most producers should notice a difference within the first month, with continued improvement through the second and third months. Significant results are normally measured after about six months. That is not a minimum program; it is the point where broader changes in the manure system are measured. A spray works or does not work by the next morning. Treating the crust does not, and anybody who tells you otherwise is selling something else.

The dosing benchmark is straightforward. Hog operations commonly start around one gallon per month per 1,000 head, about four gallons a month for a 4,000-head finishing barn. Cattle and dairy commonly start around one gallon per 75 animals. Lagoon rates may be adjusted based on the manure already in the lagoon and the amount expected to be added each month. You can work your own numbers on the treatment rate calculator.

Carl, a livestock producer in Mankato, Minnesota, put it this way: "Since using PitCharger, we haven't had the crusting issue we previously experienced and flies are close to non-existent." A livestock producer in Mankato, Minnesota reported recovering approximately 200,000 gallons of usable lagoon capacity after treatment. That is a separate benefit from the same change: when the fiber breaks down, it stops taking up storage and it stops floating as a fly bed.

PitCharger products are formulated for specific manure-management problems. Depending on the product, formulations may include aerobic, anaerobic, and facultative bacteria, enzymes, or other specific modes of action. Not every PitCharger product uses the same ingredients or works the same way, and the product is selected based on the problem being treated. PitCharger has been on the market since 1998. PitCharger products are described as safe around cattle, horses, pets, children, and vegetation. That matters when the barn is 200 feet from the house.

If you want somebody to look at your barn dimensions, head count, pit volume, and current fly counts and tell you what a program would look like, get a treatment plan. There is no cart and no public price list. The line around here is: why buy something that you hope works.

Frequently asked questions

Will treating the pit get rid of all my flies?

No single practice does. Pit treatment removes the largest breeding surface on most confinement operations, which is the piece a sprayer cannot reach. You will still want traps, sanitation around feed spills, and a targeted residual application for the adults that move in from outside. What changes is that you stop losing ground every week.

How fast will I see fewer flies?

Most producers notice a difference within the first month. The crust breaks up gradually, and the fly count follows the breeding surface, not the other way around. Producers typically notice the surface changing before they notice the fly count changing.

Does it work in a cattle barn or only in hog pits?

Both. The mechanism is the same anywhere undigested fiber accumulates in stored manure. The dosing and the application point differ. See cattle barn applications for how it is handled on scrape and flush systems and under slats.

Is it safe to use with animals in the barn?

Yes. It is a biological product, not a caustic chemical, and it is safe around cattle, horses, pets, children, and vegetation. It goes in through the slats or the pump-in point with animals in place.

What about the gas that comes out when the crust breaks up?

That is worth understanding before you agitate. Gas trapped under a mat releases in a slug when the mat is disturbed, which is a different and more dangerous situation than gas releasing steadily off an open liquid surface. Read what hydrogen sulfide and ammonia do in confinement before your next agitation, and do not shortcut ventilation regardless of what is in the pit.

Terms used here are defined in the manure management glossary. Reference material on fly biology and thresholds is available from University of Minnesota Extension and Iowa State University Extension and Outreach.