Management to Reduce Horn Flies


Mark Z. Johnson, Oklahoma State University Extension Beef Cattle Breeding Specialist

 

One of the realities of beef production in Oklahoma is dealing with significant fly populations.  The Oklahoma beef cattle industry loses millions of dollars each year due to external parasites.  Blood loss, irritation and annoyance lead to reduced levels of performance due to flies. Horn flies are considered the most important external parasite of cattle causing an estimated $1.8 billion impact on the cattle industry as a whole annually. Although this fly is small and feeds from the back down the side and onto the belly of cattle it is the sheer numbers of these flies on a per animal basis that cause stress to cattle. Considering that an individual Horn fly will feed on an animal 25 times per day, large numbers of flies will certainly cause significant stress. In a cow – calf system the horn flies on the cow or heifer impact weaning weights in calves due to the impact of that stress causes decreased milk production but when combined with direct fly numbers on the calf then the impact can be greater. 

 

Recent rains, humidity and warmer temperatures mean that Oklahoma now serves as an ideal breeding ground for these annoying -pests that rob profit potential. Horn flies are holometabolus, meaning they have complete life cycle (egg, larvae, pupae, adult). The females need a blood meal to reproduce. Horn flies are a greater problem in pastured cattle because the females need an intact fresh manure pad to complete the life cycle. The life cycle can be completed as quickly as two weeks.

 

Management To Control Horn Flies

For Horn flies, there are many different options to control this pest. Several measures can be taken immediately to control Horn flies this year.

 

  • Begin feeding an Insect Growth Regulator (IGR) now. Typically used as an additive to a mineral supplement, an IGR passes through the digestive system and into the manure where horn flies lay eggs.

 

  • Pull a drag harrow through pastures to break up manure piles. In areas where cows concentrate or at spots where hay has been fed through the winter, burning (if possible), harrowing or disking can help break up the spots where flies will lay eggs.

 

  • As you observe larger populations of flies on cattle over the next few weeks (over 200 flies per animal), start using additional control strategies. Since Horn flies spend their life on the cattle, insecticides can be highly effective. This fly behavior can also lead to issues with resistance. Resistance to insecticides can develop because Horn flies reproduce multiple generations over the summer months. Use a rotation of insecticides to avoid resistance from year to year.

 

  • Insecticides can be effectives as an insecticide ear tag, administered as a pour on or spray on. Self-application devices such as oilers can be effective if you make it a force use system or put multiple oilers out to ensure the whole herd is treated properly. A typical force use system is setting it up where cattle have to go under the oiler to get to water or a feed area.


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