Shoo Fly, Don’t Bother Me (Fly Control in Beef Cattle)

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It is that time of year when we have to worry about fly control in our herds. We talk a lot about integrated pest management (IPM) and fly control is one place where it is critical. One thing to remember, you will never have 100% fly control, but you can manage them.

The first step is to know what flies are the problem so you can decide control fliesmethods and timing. There are several flies that are a concern in beef cattle. The horn fly is considered the most economically important fly pest in beef herds. Horn flies are biting flies that feed on cattle and cause blood loss, annoyance and reduce calf weaning weights. Horn fly presence is temperature dependent, while abundance is influenced by humidity and precipitation. So during wet and humid weather, populations peak. Other flies of importance include the face fly, stable fly, house, horse fly and others. This article will discuss options for horn flies. There are many control options available, but unfortunately, none are permanently effective. Using combination methods is most effective.

The recommended threshold to start treating cattle is when levels reach 200 flies on the cow. It is best to look at multiple cows to determine when to start treating, not just one cow.

Topical sprays/pour-on products are the quickest method to knock down fly populations. Most labeled products do a good job, but they have the shortest residual control of the methods. They are considered a secondary method especially for early and/or late season control. Pour-on dewormers are included here and offer 2-3 weeks of effective fly control if timed correctly.

Back-rubs have been used for a long time and work very well if managed correctly. First, they must be set-up in an area where cattle pass-through regularly (gate between pastures, in front of a water trough, a mineral feeder, etc.). Second, you must rotate the charging chemicals from year to year and keep charged regularly throughout the summer.

Insecticide Ear Tags or fly tags are easy to use and are one of the longer acting methods of controlling flies, but resistance is a concern. There are many brand names and active chemical ingredients available. The three main chemical classes are Pyrethroids, Organophosphates, and Endectocides. No matter which fly tag you use, here are some tips.

  1. Tags have a limited lifespan, so use them when threshold numbers approach 200 flies (June time frame).
  2. Rotate insecticide chemical classes. Don’t use the same insecticide year after year. Read the label to know the active ingredient . There are several different chemicals within the same class, so switching the brand may not switch classes.
  3. There has been much documented resistance of flies to fly tags over the years, especially with the Pyrethroids, but rotating between chemical classes every year will spread out this resistance greatly.
  4. Remove insecticide ear tags when they are no longer effective, when the label recommends or in the fall.

IGR Minerals (Insect Growth Regulator) and similar products have been in use for 20+ years. They are additives that can be given in several forms including through minerals or boluses. They reduce the number of fly eggs hatching in manure and hay piles. For operations that do a good job with their mineral program and is either isolated or surrounded by cooperating farms, this system works well. The downside of feed-through products is that they work by controlling the fly population in a very specific area. If you are in an area with several other cowherds not using an IGR product, you cannot control the area population effectively.

Walk-through Fly Traps have been around for a long time, but have made a comeback due to organic, all natural beef and dairy farms. There are several designs and they work by brushing the flies off the backs as the cows walk through a gate area. At the top of the trap is a box made of transparent material (such as Plexiglas) that traps the flies as they naturally fly up to try to get out. The advantages are the trap does not use any chemicals, so resistance should not occur and it works well all season long. The biggest disadvantage is price and availability. Lower-end models will cost several hundred dollars initially and require regular up-keep. Cattle must pass through for them to be effective.

Putting it altogether – No matter what system you use, rarely does one method give you complete control. Most farms that do a good job controlling flies will use a combination of two or more of the above methods. Decide what works for your operation considering time, money, and how you manage your cattle. For more information, call your Extension Agent.

NCSU Extension