Whether in a pasture or a barn, fly control is an essential part of keeping healthy dairy and beef cattle herds.
In pasture cattle the two primary fly pests are horn flies, which are a biting fly, and face flies. Face flies do not bite, but they feed around the eye tissue and can transmit bacterial conjunctivitis, or pinkeye.
"Horn flies are the No. 1 fly pest in the United States," says Purdue University entomologist Ralph Williams. "The threshold at which we recommend control is when those flies reach 200 per animal. It is not uncommon to see a thousand or more horn flies per animal." While horn flies do not transmit disease, they can cause economic loss by reducing weight gain, feed efficiency and calf weights.
Taking proper steps to control flies is essential for livestock health
For cattle in confinement, the stable fly is a biting fly that breeds in the accumulating feed waste and soiled bedding. There's no disease associated with them, but they, too, can result in economic loss.
Houseflies are the other common confinement pest. While they're not directly associated with cattle, they can be a nuisance to people and surrounding neighbors. "In confinement flies are best controlled through sanitation," says Williams. "Farmers should identify and remove fly breeding sites such as manure and soiled bedding."
In the pasture, however, fly control is a bit more challenging. Insecticides can be effective as long as they stay on the animal for an extended time. One such method is through pesticide ear tags.
Which type of ear tag is best to use for cattle on pasture?
"For flies in pasture, insecticide ear tags are really the most suitable to control both face flies and horn flies," says Williams. "Some of the products available are pyrethroids and organophosphates. The pyrethroid-based tags generally are not very effective for horn flies because of a genetic resistance. Most of the organophosphate tags are very efficient for horn fly control. Abamectin is a new product that is available in some tags and has been very effective for both horn flies and face flies."
Some tags also are available with a combination of insecticides that will control both face and horn flies.
Other options include self-applied dust bags in a forced-use situation, which cattle need to access daily, and pour-on insecticides, which can last up to a month. Feed-through insecticides, ingested with feed and released in the manure, also can disrupt flies. But if not all cattle in the area are using them, flies could still be present.