Horn flies cost more in loss of production than any other external parasite in the cattle industry.

These troublesome flies are very bothersome to cattle.

“(The flies) should have probably been called back flies instead of horn flies,” University of Arkansas Research and Extension specialists Johnny Gunsaulis said. “They spend most of their time riding on the back of the animal upside down.”

Gunsaulis said the weather this year has really effected the fly population.

“The wet conditions we had this spring have really caused them to be bad this year,” Gunsaulis said. “They cost lost production from cattle expending energy to swat them, spending time under trees to stay away from them, and staying huddled together for relief.”

More serious conditions horn flies can transmit are pinkeye and mastitis.

Gunsaulis said the flies can cause an irritation on teats which can lead to mastitis – even in heifers that have never been in lactation.

Most of the time, flies tend to stay on the same animal only to leave to lay eggs in the fresh manure piles on the pasture.

Flies are worse when manure piles are slow to dry and populations usually reduce in the warmer months.

Once there are 150-200 flies per animal, chemical treatment of the animals is economically justified Gunsaulis said.

There are several treatment methods available for horn flies. The tags can provide good protection for an extended period.

“When choosing tags, it is important to notice if the tag is labeled as safe for pregnant animals, note whether one or two tags is required for each animal, and you should rotate between different chemicals each year to prevent the flies developing resistance to the chemicals in the tags,” Gunsaulis said. “Some producers feel like they have less eye irritation if they put the tags on the back side of the ears instead of the front of the ears.”

The disadvantage of ear tags is there is more labor involved by having to work each animal and hold them while placing the tags. If you do use tags, it’s also important to remove them after later in the season, Gunsaulis said.

A short-term relief option would be to use a spray, however the effects aren’t as long term as the tags. However, spray also requires working the cattle, similar to the tags.

There are dust bags, rubs, and oilers that can be effective if the cattle can be encouraged or forced to use.

This treatment option uses less labor, however, it is up to the cattle how well they are treated.

Most major brands of mineral have the option to have an insect growth regulator added. Minerals should be started early in the season, maintained throughout the season, and it’s important for the animals to have good consumption of the product Gunsaulis said.

A newer method on the market is the gun, like a paint ball gun, that can be used.

“This can be an option in instances where it’s not possible to gather the animals,” Gunsaulis said. “While very entertaining, the long-term effectiveness of this method may not be as successful as the tags but it should still be considered for a lot of operations.”

For producers that are opposed to chemicals, fly traps may be an option.

Traps must be placed in an area where the animals are forced to use it two or more times per day. Gunsaulis said the product is not cheap and effectiveness is questionable.

Different breeds of cattle are effected by flies differently. Brahmans, for example, are more naturally resistant to flies than other breeds.

For most operations, a mix of techniques is most likely the best defense against horn flies Gunsaulis said.

While selecting a treatment best for the operation, consultation with a veterinarian or extension agent is always best.


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