Fly Control – Lessening the Burden

— Written By Tom Devine and last updated by
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Cow with lies on faceAn out of control fly population can cause economic losses to a beef cattle operation by decreasing the grazing efficiency of our cows, hindering weight gain of our calves and creating pink eye issues. In North Carolina, there are three major species of flies that impact performance of our cattle: the horn fly, face fly and stable fly. 

  • Horn flies cause the most economic loss of the three. They are small in size and normally found on the poll area, back, side and belly of cattle. One horn fly will consume roughly 30 blood meals in a day, resulting in a population of just 500 horn flies removing a pint of blood per day. It is not uncommon to find 2000-5000 horn flies on untreated cattle. 
  • Face flies are non biting flies that closely resemble the common house fly. They gather around the eye and mouth and feed on animal secretions. Face flies make cattle more susceptible to pinkeye because they damage eye tissues while feeding on secretions from the eye. 
  • Stable flies are blood feeders that cluster on the front legs of cattle. They have a very painful bite and cause cattle to stomp their legs and stand in water to prevent being bitten. If stable flies are not treated, cattle will spend most of their day trying to avoid being bitten, instead of grazing. 

Controlling these flies can be difficult and what works on one farm may not work on another. So what can we do? First, we need to know what kind of fly control methods are available for use then, understand the positives and negatives of each. There are several fly control methods out there from hand applied dusts, pour-ons and prays to rubs ear tags and feed additives. 

  • Most hand applied dusts and sprays work very well at controlling fly. However, they require frequent applications and can become very labor intensive. 
  • Rubs are a very effective and economical method for controlling flies if cattle are forced to use them. Some cattle will voluntarily use them but some will not. So placing them in an area where cattle must use them and keeping them charged is key. Rubs should be recharged every 2 weeks. 
  • Fly tags, especially newer generation fly tags, work well at controlling fly population. Most fly tags require an application of two tags per adult cattle and one tag per calf. Producers should wait until they notice a population of about 200 flies per cow before using fly tags. To reduce the chances of flies becoming insecticide resistant, producers should use pyrethroid tags for two year and  then switch to organophosphate tags for one year. Tags should be removed 5 months after they are applied to further help prevent insecticide resistance. 
  • Pours-ons and fly tags can be applied at the same time to save time and labor. Pour-on dewormers offer dual parasite protection by killing internal parasites while helping to control fly populations. However, multiple applications of pour-on dewormer throughout the year can cause internal parasite resistance issues. Pour-ons labeled for external parasites only should be used for re-applications.
  • Feed additives are very effective at disputing the fly life cycle resulting in decreased fly population. Larvicide and insect growth regulators can be fed to cattle through a ration or free choice mineral, starting 30 days before the emergence of flies to 30 days after a hard frost. If you plan to use a feed additive to control flies, keep in mind that some flies can travel 1-2 miles. So if your neighbor is not using a fly control feed additive, you may inherit some of their flies.

It is impossible to completely eliminate a fly problem in our cow herd. Using one of these methods alone will not give you the results you are after. Using multiple methods is the best way to help lessen this burden that our cows face.