Biological fly control is a proven way to control flies before they become the adult pests that can spread disease and bother you and your horses. These tiny gnat sized fly parasites, also commonly called predators, deposit their eggs in the fly pupa and destroy the immobilized fly during its pupal stage, long before it can become an adult pest. As well by reducing the use of harmful chemicals, natural systems of beneficial predators can flourish.
Organic Cowboy Fly Control Usage
Locate your worst fly breeding habitats
The primary fly breeding habitats in horse stables are those areas where manure builds up along fence lines (tough to clean up areas), and where manure is stored for later removal or handling. These are the primary fly breeding habitats and this is where you’ll find fly larva in large concentrations.
Put your fly parasites to work
It’s now time to release your fly parasites and let them go to work for you. Working along the fence line, choose the areas of greater build-up, then simply peal open the top of the pack and shake out a small quantity of the fly parasites on to the manure. Continue with this process, until you’ve covered as much of the stable as possible. As the season progresses, you’ll begin to clearly recognize the worst fly breeding habitats. You should release your fly parasites there first, and then move to the secondary habitats. This is the same procedure you’ll follow with the arrival of each shipment of Organic Cowboy™ Fly Parasites.
Maintain an effective program
Your fly parasites are now doing their job, but there are things you can do optimize your season-long fly control. Along with releasing the proper number of fly parasites throughout the season, weekly stall and barn cleanup can greatly reduce the amount of fly breeding habitat and effectively interrupt the fly breeding cycle. Cleanup and limited spray use in fly roosting habitats (where adult flies rest), can complement your biological fly control program. Just be sure never to apply the chemical sprays in areas where you release your fly parasites.
Frequency
Whether you choose to receive your fly parasites every other week or monthly, be sure to release them within 48 hours of arrival.This helps you stay ahead of the flies, and insures that the fly parasites are fresh and ready for action. If you choose to store them for a few days, keep them refrigerated, to slow their metabolism.
Frequently Asked Questions
Fly parasites (also called predators) are tiny, gnat-sized beneficial insects that naturally control fly populations by targeting flies before they hatch. They lay their eggs inside fly pupae, preventing adult flies from ever emerging.
This breaks the fly life cycle at its source—making it one of the most effective long-term solutions for horse barns.
Yes. Fly parasites are completely safe and non-invasive. They do not bite, sting, or bother horses, humans, dogs, or other animals.
They only target fly pupae and are considered an eco-friendly alternative to chemical sprays.
Fly parasites should be placed in areas where flies breed, including:
- Manure piles
- Stall bedding
- Fence lines
- Compost or waste areas
These are the primary locations where flies lay eggs and develop.
Most customers begin noticing a reduction in flies within 2–4 weeks, with continued improvement over the season.
Because fly parasites work by interrupting the life cycle, results build over time rather than instantly.
For best results, fly parasites should be released regularly throughout the fly season, often weekly or bi-weekly depending on your climate and infestation level.
Consistent releases ensure continuous control as new flies attempt to hatch.
No solution eliminates 100% of flies. However, fly parasites will have a substantial impact on your fly population.
They are best used as part of an integrated fly management program.
Fly parasites are a species-specific parasitoid effective against common barn and stable flies, including:
- House flies
- Stable flies (biting flies)
- Horn flies
- Blow flies
They target flies that breed in manure and organic waste.
As a natural approach fly parasites offer several advantages over chemical sprays:
- No toxic residues
- No resistance buildup
- Safe for animals and the environment
- Long-term population control
Unlike sprays that kill adult flies temporarily, parasites stop future generations from developing.
Most people never notice them. They are extremely small and work quietly under the surface of fly breeding areas.
You'll notice fewer flies, not the parasites themselves.
Yes. For best results, combine fly parasites with:
- Manure removal
- Proper drainage
- Fly traps or physical barriers
Integrated strategies provide the most effective control.
Yes, but effectiveness depends on timing and consistency. Most programs are tailored to your region's fly season and temperature patterns, ensuring optimal results.
Getting started is simple:
- Identify your barn size and fly problem level
- Begin early in fly season
- Follow a consistent delivery and release schedule
The Organic Cowboy offers customized seasonal plans with automatic shipments for your convenience.
Frequency and quantity of application are critical to your programs success
Matt Grainger has been working with biological fly control since 1874, when he first began pioneering the use of fly parasites throughout Colorado, Kansas, and Nebraska. Over the past five decades, he has worked alongside horse owners, boarding and training facilities, cattle feedlots, dairies, poultry operations, and livestock producers across the country, helping them solve one of agriculture’s most persistent challenges—flies.
As the owner and operator of Organic Cowboy, Matt has built his career around practical, science-based solutions that work in the real world. Rather than depending solely on chemical insecticides, Organic Cowboy develops customized fly control programs that combine parasitoid wasp releases with proven Integrated Pest Management (IPM) practices. Every operation is different, so Matt focuses on prevention, habitat management, biological control, and targeted intervention to create long-term, sustainable results.
After more than 50 years in the field, Matt’s approach continues to help producers achieve season-long fly control. His hands-on experience, combined with decades of refining best practices, has made Organic Cowboy a trusted resource for effective, environmentally responsible fly management.
The science of fly parasites
Fly parasites are a species-specific parasite, laying their eggs exclusively in fly pupa providing control of house flies, stable flies and horn flies. Learn more about the science of organic fly control.