External parasites can be costly for cattle producers and getting a handle on problems early can lead to more prosperous and better performing cows. Examples of bloodsucking flies include the horn fly, stable fly, horse fly and deer fly.
Horn flies are a common problem battled by cow-calf producers. Negative effects are decreased weight gain and the consistent irritation caused by flies lying and feeding on the backs of cattle. Cows use up energy by trying to flee the flies. This leads to reduced profitability.
For ranchers, the first step in their fly control program should be identification of the external parasite. Ranchers should ask themselves the following questions. How big of an external parasite problem do I have? Does it have economic implications? What method or methods can I use to control them?
Activity varies among different flies. While the horn flies rest on the back of the cows, stable flies remain on the cow only while feeding and feed mainly on the legs.
According to Dr. Jason Cleere, Texas A&M AgriLife Extension Service beef cattle specialist at College Station, the horn fly is the most damaging because they do suck blood and reduce the performance of the cow. Adult flies live for about three weeks and feed up to 30 times per day. They lay eggs profusely, especially around manure piles. Within nine to twelve days reproduction can occur. The biggest flushes of flies usually come in when there is moderate temperatures and recent moisture.
Peak populations for horn fly are late spring and early fall. The economic treatment level is approximately 250 flies per animal. Treatments include pour-on, sprays, ear tags, feed additives, dusts and rubs. Cultural remedies can include removing fresh manure from barns and stalls and preventing buildup of wet, decomposing vegetation such as hay. Keeping barns clean and manure clear will be a producer’s biggest ally in controlling flies in those areas.
Biological control includes parasitic wasps, which are fly predators and are effective but not viable on a large commercial cattle production scale since there are large numbers of animals in a herd. Chemical horn fly control includes ear tags, pour-ons, sprays, feed additives, boluses, dust bags, rubs and gel caps. Pyrethoids, organophosphates, organochlorine and abamectin are some topical products. Oral products are insect growth regulator (IGR) and organophosphates.
Producers deworming using a pour-on are getting a decrease in fly populations for about thirty days. The challenge with rubs is getting the cattle to use them. If a rancher has some areas where cattle are traveling back and forth, rubs are certainly a valid option.
Ear tags provide about 90 to 150 days of control. Fly season typically lasts longer than this. Ear tags also require putting the cattle in a chute. Feed additives in mineral supplements cost about $4.50 to $8 per head a year if the cow is eating a bag of mineral a year.
For more information about this topic, contact the A&M AgriLife Extension office of Clay County (940) 538-5042.