Whole Animal Sprays

• Sprays containing pyrethrums can be applied to cattle and other animals after removing dirt and dust from their coats. Whole-animal sprays are a fast way to relieve horn fly attacks. Brush the animal's hair while spraying on the insecticide until the surface of the hair is wet. Don't wash treated animals where there's runoff because pyrethrums are toxic to fish. Still, pyrethrums are considered a natural pesticide and are made from chrysanthemums and other related flowers.
  
  

Self-Applicating

• Dust bags and back rubbers contain man-made insecticides like pyrethroids and organophosphates. Pyrethroids are similar to pyrethrums, and organophosphates are chemicals that disrupt an insect's nervous system. Back rubbers and dust bags are placed in areas of restricted movement, like gateways that the animals must pass through on their way to feed and water. When the animals make contact with them, the back rubbers and dust bags release insecticides that are very effective in controlling horn flies.
  
  

Feed Through

• Insecticidal additives can be added to animal feed or mineral blocks to control horn fly larvae, but they have no effect on adult flies. Two types of additives are available. Insect growth regulators, including diflubenzuron and methoprene, prevent larvae from maturing into adults, and larvicides like tetraclorvinphos kill larvae.
  
  

Controlled Release

• Ear tags containing insecticides like synthetic pyrethroids and organophosphates can be used to control horn flies for approximately 12 to 15 weeks by releasing small amounts of insecticides over a period of time. Unfortunately, some horn flies have developed a resistance to ear tags. Ear tags are more effective if you rotate chemicals rather than using the same one all the time.
  
  

Parasites

• Horn flies can also be controlled by introducing parasitic wasps into your barn. These tiny wasps are the size of gnats. Although it's not possible to completely eliminate horn flies with parasites, they do reduce the amount of chemical pesticides needed for fly control. In addition, using parasites helps to keep horn flies from building up a tolerance to pesticides. The type of wasp to purchase varies, depending on where you live. Consult your local county extension for information about which species is right for your area. Other horn fly predators include dung beetles.