Q. What are the best and most effective ways to control flies on beef cattle? (July 6, 2012)
A. There are many different fly control products available for cattle producers to use. The key to fly control is to apply it on a timely basis and don't use the same active ingredient for more than two years in a row. The reason for this is that flies will become resistant to the active ingredient if used over and over again.
I see producers put fly tags in way to early because of convenience when there are no or few fly and then have no control later in the season. If you are using fly tags, put them in a week to 10 days before the fly season starts. I know this is a guess – but in Nebraska, we usually don't have fly problems in April. If fly problems are bad, it may mean you put a tag in the cow and calf.
Sprays and oilers are effective as well. If you use an oiler, make sure the height is so calves can also use it. Not all oilers are built the same, so check construction.
Make sure about every two years that you use a tag that has a different active ingredient. If you don't change active ingredient, flies will become resistant and this fly control method will not work.
There are sprays that you can use and are effective for two to three weeks then you will need to spray again. Some producers use this method and when they move the cows to a new pasture in their rotation, fly spray the cattle.
Also available are oilers that can be filled with a fly control ingredient. Cattle rub the oiler and dispense the fly control.
Finally, there are dust bags that contain a fly control and the cattle rub against the bag and the dust is applied to the animal. Dust bags need to be put in a place where cattle frequently visit like a watering area. Put the bags down low enough that the dust can be applied to the face and calves can use them.
Also, if there are areas that stay wet and are breeding grounds for flies, see what you can do to eliminate them.
IGR products are Insect Growth Regulators and they control flies at the site the eggs are deposited — manure. Face flies and horn flies lay their eggs in cow manure and the larvae only develop in cow manure. Therefore, some of the compounds are fed or given in bolus form that kill the larvae in the manure pat. Examples of this include the slow release bolus with diflubenzuron (Vilgilanteâ). This compound is an insect growth regulator (IGR), which is safe, and cross-resistance does not develop. Another IGR that is used in "feed through" products is methoprene. Other products are available that can kill the fly larvae when used as a "feed through". Flies do travel some distances, so you may use these products and still have flies that come from your neighboring pastures. If your neighbors use an IGR, then you potentially will have fewer flies.
For more information, please see the Controlling Flies on Pastured Cattle article.
Source: Dr. Rick Rasby, Professor of Animal Science, University of Nebraska