Alicia Boor: How to combat stable flies

Hays Daily News
Alicia Boor

Stable flies (Stomoxys calcitrans) are starting to emerge with the start of spring; you might even have seen a few around already! Stable flies are distinguishable by four black stripes on the thorax, black checkered spots on the abdomen and large, protruding mouthpart.

These flies are a common pest feeding primarily on cattle and horses but can also target other livestock species, pets (especially dogs) and humans. Both male and female adult flies are obligate blood feeders and their painful bite and feeding causes significant annoyance and blood loss. Stable flies can negatively affect cattle average daily weight gain, milk production and feeding efficiency. Each fly feeds once or twice a day for between two and five minutes each time.

Stable flies are routinely found on the legs or underside of large animals such as horses and cattle, on dogs and small ruminants however, they are generally found around the head area. When not feeding, adult flies can be found resting on building surfaces or vegetation. Sustainable stable fly control is best achieved through an integrated approach.

In her lifetime, a single adult female can lay between 500 and 1000 eggs. Limiting resources available for egg laying and larvae development, especially in the spring and summer months is essential. Stable fly larvae develop in decaying plant matter, particularly those contaminated with animal waste. Hay bales are a great breeding site for stable flies, elevating hay and straw off the ground when feeding animals prevents manure and urine contamination.

Periodically clear feed storage and animal feeding areas of spilled hay, straw and feed. Large bales for herd feeding are especially able to promote fly populations, be sure to inspect and clean these areas regularly. Separate animal watering from feeding areas and protect stored feeds from weather and water runoff. For areas where straw bedding is used, frequently replace the bedding, spreading decomposing waste in thin layers, which allows waste to dry faster and be less attractive to female stable flies.

Composting manure increases heat and dries out material making the environment inhospitable for developing fly larvae. If you have to store manure waste in piles, attempt to keep as little fibrous plant material/feed as possible in the pile.

Insect growth regulators fed to animals as feed-throughs inhibit stable fly development during the pupal stage reducing adult fly numbers and are a great addition to an integrated pest management program. Adult stable flies can be controlled through insecticide application with both pyrethroid and organophosphate products being effective although resistance to both is increasing.

For more information on specific products to use, search the VetPestX website for specific product information (

Alicia Boor is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact her by e-mail at or calling 620-793-1910.