Nobody talks about flies when they talk about pig farming. They talk about feed conversion, breed selection, disease management, and market prices. Flies get mentioned as an afterthought, if at all, usually in the context of general farm hygiene rather than as a serious production problem in their own right.

That is a mistake.

On a Nigerian pig farm operating without active fly control, a single sow pen can harbour tens of thousands of houseflies and stable flies during the rainy season. Those flies are not just unpleasant. They are actively costing that farmer money every single day through stress-related feed inefficiency in growing pigs, disease transmission between animals, wound myiasis in piglets and sows with skin injuries, and the very real risk of regulatory or buyer rejection for farms supplying hotels, restaurants, and processed meat operations that conduct farm audits.

Fly control on a pig farm is not about comfort. It is about profit.

Two Flies, Two Different Problems

Most pig farmers treat all flies as the same problem requiring the same solution. They are not.

The housefly Musca domestica and the stable fly Stomoxys calcitrans are the two species responsible for most fly-related production losses on African pig farms and they cause completely different types of damage requiring different management responses.

Houseflies do not bite. They feed on manure, feed waste, and organic matter around the pig unit and transfer bacteria, viruses, and parasites between their feeding sites and the pigs, feed, and water they subsequently land on. Their primary damage is disease transmission. African swine fever, swine dysentery, and various intestinal parasites all have documented transmission routes through housefly mechanical carrying. A pig farm with a heavy housefly population is a farm where pathogen movement between pens is happening constantly and silently.

Stable flies bite. They feed on blood and they feed aggressively, biting the legs and flanks of pigs repeatedly. Each bite causes pain that disrupts feeding behaviour. Pigs under stable fly attack spend time and energy moving away from flies, bunching in corners, and stamping rather than eating and growing. Research on pig production under stable fly pressure consistently shows reduced average daily weight gain of between eight and fifteen percent compared to fly-free controls. On a farm growing pigs to market weight that difference is measurable in both time and money.

Identifying which fly is your primary problem before spending money on treatment saves both time and resources. Houseflies rest on walls, ceilings, and surfaces around the farm and are visible throughout the day. Stable flies rest on the lower walls and outside surfaces of pig buildings and are most active in the morning and late afternoon. If your pigs are showing leg stamping and bunching behaviour, stable flies are your primary issue. If disease incidence is high but pigs are not showing fly-avoidance behaviour, housefly-transmitted pathogens may be a contributing factor worth investigating.

The Manure Management Truth Nobody Wants to Hear

Every fly control product, spray, trap, and treatment method available to Nigerian pig farmers will fail if the underlying manure management on the farm is inadequate.

Housefly larvae, the maggots that become the adult flies causing your problems, develop in wet manure. A single pile of wet pig manure left undisturbed for five to seven days in warm Nigerian conditions can produce thousands of adult flies. Those adults lay more eggs in more manure and the population compounds rapidly. Spraying adult flies without addressing the breeding site is like bailing water from a boat without closing the hole. You can spray every day and still have more flies tomorrow than you had yesterday if wet manure is accumulating faster than your spray kills adults.

Remove manure from pig pens every two days during the rainy season and every three days during the dry season. This interval is critical because housefly larvae require five to seven days in the manure to complete development to the pupal stage. Removing manure every two to three days removes the larvae before they can complete development and emerge as adults. Composting removed manure in a dedicated area at least 30 metres from the pig unit allows natural heating of the compost pile to kill any remaining larvae and pupae.

Manage pen drainage so that water from drinking, washing, and rain does not pool in or around pens. Wet manure supports fly breeding at a rate far higher than dry manure. Simple drainage improvements, sloping pen floors toward a central drain, maintaining drainage channels around the unit, and covering feed storage to prevent moisture contamination, reduce fly breeding habitat more effectively than any chemical treatment applied without these basic measures in place.

Treatment Methods That Work in Nigerian Conditions

Residual Wall Sprays

Cypermethrin 10 EC applied as a residual spray to the walls, ceiling, and surfaces of pig housing kills flies that land on treated surfaces for up to four weeks after application.

Mix cypermethrin 10 EC at 10ml per litre of water. Remove pigs from the unit before application. Apply using a compression sprayer set to a coarse spray that wets surfaces without excessive runoff. Cover all wall surfaces, ceiling areas, door frames, and any surfaces where flies rest. Allow to dry completely before returning pigs to the unit, typically two to four hours depending on ventilation and temperature.

Repeat every three to four weeks or when fly activity increases noticeably between scheduled treatments. Do not spray into feed or water containers. Cover all feed and water equipment before spraying and clean thoroughly before returning to use.

Bait Stations

Fly bait stations placed around the pig unit perimeter attract and kill adult flies through a combination of food attractant and insecticide. They are particularly effective against houseflies and significantly reduce the adult population without requiring repeated whole-unit spraying.

Commercial fly bait granules containing imidacloprid or methomyl are available at veterinary and agro-chemical suppliers in Lagos, Abuja, and Port Harcourt. Place bait in shallow containers or on flat surfaces around the outside perimeter of pig buildings, near manure storage areas, and at entry points to the farm. Keep bait dry and replace every two weeks or when it becomes wet or contaminated.

For a low-cost homemade bait, mix 100 grams of sugar with one litre of water and add 10ml of trichlorfon insecticide solution. Pour into shallow containers placed around the farm perimeter. The sugar attracts flies and the trichlorfon kills them on consumption. Replace every three to four days.

Larval Control in Manure

Treating manure directly to kill fly larvae before they emerge as adults is the most efficient point of intervention in the fly life cycle.

Diflubenzuron, an insect growth regulator sold under brand names including Dimilin, prevents fly larvae in treated manure from developing to the adult stage by interfering with chitin synthesis during moulting. It is mixed into pig feed at label-specified rates and passes through the pig’s digestive system into the manure where it kills larvae. It has no effect on the pig itself and leaves no harmful residue in pig meat or waste. It is available through veterinary suppliers and is registered for use in pig production in Nigeria.

Where diflubenzuron is not available, cyromazine feed-through larvicide works through the same mechanism and is available as a feed additive through some veterinary supply chains in Lagos and Abuja.

Fly Traps

Large sticky fly traps hung inside and around pig buildings capture significant numbers of adult flies without chemical application and are useful as both a control measure and a population monitoring tool.

Hang sticky traps at pig shoulder height inside buildings where flies concentrate and replace when covered. For outdoor use hang traps near manure storage and at building entry points.

Ultraviolet light traps placed inside pig buildings attract and electrocute flies drawn to the UV light source. They are more expensive than sticky traps but more effective in enclosed spaces and require only periodic cleaning rather than replacement.

You can also read: Common poultry pests in Nigerian farms and how to treat them

Wound Myiasis: The Fly Problem That Kills Pigs

Wound myiasis deserves specific attention because it moves fly damage from a production problem to a welfare and mortality issue.

Myiasis occurs when blowflies, primarily Chrysomya species, lay eggs in open wounds on pigs. The eggs hatch within 12 to 24 hours in warm conditions and the larvae begin feeding on wound tissue, extending the wound and causing severe tissue destruction. A small wound from a bite, injection site, or farrowing injury that goes uninspected for two to three days can develop into a life-threatening myiasis infestation in hot humid Nigerian conditions.

Inspect every pig in your unit every day. Any wound regardless of how small must be treated immediately. Clean the wound with diluted iodine solution, apply wound spray containing cypermethrin or permethrin to repel flies from the wound site, and mark the animal for daily monitoring. Established myiasis with visible larvae requires manual removal of larvae with tweezers followed by thorough wound irrigation with diluted iodine and immediate veterinary consultation for severe cases.

Prevention is straightforward. Treat all wounds immediately. Castration and tail docking wounds in piglets must be treated with wound spray on the day of the procedure and monitored for three to five days. Do not leave injured or sick animals in communal pens where wounds are exposed to the high fly pressure typical of pig housing.

Seasonal Adjustments Every Pig Farmer Should Make

Fly pressure on Nigerian pig farms follows a predictable seasonal pattern that allows you to prepare rather than react.

The rainy season between April and October is peak fly season. Wet conditions accelerate manure moisture content, increase breeding site availability, and extend the adult fly activity period. Increase manure removal frequency to every two days during this period. Begin residual wall spray programme at the onset of the rains in April before fly populations build. Check and replace bait stations every two weeks without fail.

The dry season between November and March brings lower fly pressure but does not eliminate it. Maintain a monthly residual spray schedule during the dry season and continue manure management practices. Use the dry season to repair drainage infrastructure, seal cracks in pen walls that serve as fly resting sites, and clean and disinfect the entire unit during any destocking period.

Conclusion

Fly control on a pig farm comes down to one decision made consistently every week. Remove the manure before the larvae inside it become the flies above it.

Everything else, the sprays, the traps, the baits, the larvicides, they all work better and last longer when that one foundational practice is non-negotiable on your farm. A pig farmer who removes manure every two days and applies a residual wall spray monthly will spend less on fly control and have fewer flies than a farmer who sprays every week but leaves wet manure sitting in pens for a week at a time.

Fix the breeding site first. Then treat the adults. In that order, every time.