Flies on cattle
Updated: August 4, 2021
By Sarah Potts

Although the weather has been unseasonably cool through April and May, it’s not too early to start thinking about fly control.  There are three major types of flies with economic significance to the U.S. beef and dairy industries.  These include horn flies, face flies, and stable flies.

The horn fly is a biting fly that causes significant irritation to cattle on pasture.  The horn fly can cause avoidance behaviors, such as bunching, that reduce feed intake, increase energy expenditure, and reduce daily gains.  The horn fly is typically found on the back or topline of the animal during the cooler morning hours and on the underside or belly during the warmer afternoon hours.  It is recommended that producers monitor the horn fly load once per week during the mid-morning hours when the flies can be easily observed on the back of the animals.  If there appear to be more than 200 flies per animal, treatment is needed to reduce economic losses. 

The face fly is a non-biting fly that also impacts pastured cattle.  This fly feeds on bodily secretions found around the eyes, nose, and mouth, causing significant irritation.  The face fly also serves as a vector for bovine keratoconjunctivitis (pinkeye) and infectious bovine rhinotracheitis (IBR).  Pinkeye is a highly contagious bacterial infection of the eye and IBR is a severe viral respiratory infection.  Both conditions cause reductions in productivity.  Controlling face fly numbers, in addition to vaccination and quarantine protocols, can help prevent widespread pinkeye and IBR infections in the herd.  If there are more than 10-15 flies per face, it’s time to re-examine your face fly control measures.

The stable fly, like the horn fly, is also a biting fly that causes irritation to the animal.  These flies tend to accumulate on the front legs of cattle and provoke avoidance behaviors, such as foot stomping and tail switching, which negatively impacts feed intake and daily gains.  The stable fly prefers to lay its eggs in decaying organic matter, such as manure or old feed, so regular removal of this material from barns and around feeders and waterers can help control these flies.  If there are more than 5 flies per leg, you should consider additional fly control methods.

There are several approaches to controlling flies and some are more effective than others depending on the type of fly you wish to control.  Cleaning up accumulated manure or decaying organic matter around sacrifice areas or barns can help prevent excessive fly populations simply by removing their nesting areas.  This is especially true for stable flies, which are difficult to treat because of their affinity to the legs of the cattle.

Back rubs or dust bags that include an insecticide are effective in controlling both face and horn flies.  These methods are most effective when incorporated into a forced-use system, where cattle must come into contact with the insecticide in order to receive water, feed, or mineral.    

Fly tags are also effective in controlling both horn and face flies.  When using fly tags, all adult cattle should be tagged at once and the class of insecticide should be rotated from season to season to help prevent insecticide resistance.  Tags may not necessarily maintain their effectiveness throughout the entire fly season and might need replacement before the fly season is over. 

Oral larvicides can be effective in keeping horn fly numbers in check and are usually mixed with mineral or feed so that animals consume them on a daily basis.  The caveat with this method is that each animal must consume an adequate dose on a daily basis in order for it to be effective.  This can be difficult to guarantee in group- or free-choice feeding situations. 

A pour-on insecticide can also help control horn flies.  When using a pour-on, each animal should be weighed to determine appropriate dose.  This method is more labor-intensive than other methods because the drug must be reapplied every few weeks throughout the fly season and animals must be restrained for each application.

Use of insecticide spray is another approach that can help control horn and stable flies.  However, these sprays only work to temporarily reduce fly populations and must be reapplied every few weeks throughout the season. 

Often, a combination of fly control measures will be the most effective.  If one method does not seem to be working, double check to make sure that it is the right approach for the type of flies you see on your cattle.  Make sure the proper dose of insecticide is being administered to the animals at each application.  Furthermore, implement cleaning procedures to regularly remove decaying organic matter from sacrifice or feeding areas.  Keep in mind that it may take some trial and error before you the method(s) that works best for you and your farm. 

More Beef Resources           Printer Friendly Version