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Fly control options, explained

Tony Hawkins for Progressive Cattle Published on 23 March 2022
Fly control

Fly season is almost upon us. These little pests cause significant loss of production (aka less weight gain) and spread disease readily. If you do not control fly pressure on your livestock, you’re leaving real money on the table.

There are three big players when we are talking about fly control: the horn fly, the face fly and the stable fly. Each of these species has a different life cycle, feeding pattern and resting habits. For this reason, we must approach fly control with a variety of strategies for optimal control.

Feed-through products

Feed additives are often mixed with free-choice mineral or within the ration and contain ingredients that halt normal development of immature fly stages in the manure, which interrupts the life cycle of the flies and prevents development of future generations.

This can have a significant impact on the total number of adult flies that are present. However, there are a couple of important points to keep in mind. For the oral larvicide to be effective, cattle must consume the labeled amount daily.

Another thing to remember is: Flies don’t stop at the fenceline; adult flies can travel several miles to seek out a host. These issues can make it appear the product is not working when, in reality, it is just one tool in our fight against flies.


Rubs and dust bags provide regular application of insecticide and can be very effective with correct installation and regular maintenance. Dust bags should be hung at shoulder height (of the cattle you are treating) or lower so the cattle have to lift the bag with their head to pass under it. If they are able to get under the bag without having to lift it, you will need to lower it. The dust in the bag must be kept dry with a shelter or a protective canvas cover; otherwise it will clump and won’t dispense properly.

There are several different forms of self-applicator rubs available: back rubbers, face strips that are hung from the back rubber, fly bullets and insecticide-saturated covers for ground-level mineral feeders.

All of these rubs need to be recharged regularly with an oil-based insecticide. The frequency you will need to recharge it depends on several factors, such as rainfall and the number of animals. For these products to be effective, they must feel wet to the touch. If they feel dry or only slightly damp, you will need to add more insecticide.

When you are reloading the back rubber, do not try to pour insecticide over it while it is still hanging. Instead, take it down and coil it in an empty tub, then pour the insecticide over it and let it soak up overnight. If you have problems with face flies or pinkeye, an insecticide-saturated cover for a mineral feeder will help immensely. Do not keep the reservoir full all the time, or the insecticide will continuously wick out and drip on the ground. Instead, only fill the reservoir to recharge the lining.

Daily application of either dust bags or rubs will help ensure the maximum effect against flies. This is best accomplished by fencing off the water source or mineral feeders and hanging these products in the entrance and exit.

Producer-applied products

This is a broad class of products intended to be applied directly to the animal by the producer, and typically the insecticide is formulated to have residual activity. This category includes sprays, pour-ons and unique insecticide delivery systems.

Sprays come ready to use or as a concentrate that must be mixed with a larger volume of water or oil, and they are intended to be misted over the animal to provide complete coverage. They can be applied with a pump-up sprayer or an ATV-mounted tank sprayer and must be reapplied at regular intervals. Oftentimes, cattle are sprayed while they are grazing out at pasture, but if they are uncooperative, then you can gather them into a smaller corral to spray the group.

Pour-ons are concentrated forms of insecticide that are applied along the backline and are then dispersed to cover the entire skin surface. These products are best applied when the animals are confined tightly, such as in a narrow alleyway or chute.

Finally, there are other products with creative routes of administration, such as insecticide delivery systems that project capsules filled with insecticide that burst upon impact with the animal. This applies insecticide similar to a pour-on product.

The key to successful fly control with these products is applying a high enough level of insecticide and at a frequent interval.

Fly tags

Insecticide-impregnated fly tags are commonly used to help control horn flies and face flies. These tags release insecticide that is distributed over the animal. Fly tags are commonly applied too early because this is when it is practical to process cattle, and this will negatively impact how effective the tags control flies. To provide optimal control, it is best to apply the tags after horn flies are already active. Another important practice is to rotate annually between fly tags with different classes of insecticide to avoid development of resistance.

Premise fly control

This is a broad and diverse category that includes fly traps, premise sprays and insecticide baits. These options are intended for control of flies around a premises (barn, stable, residence, etc.), but cannot be expected to provide adequate control in a pasture setting.

Fly traps come in two styles: sticky traps and odor-attractant traps. The sticky traps catch flies that land on them, and some have patterns that attract flies to their surface. Odor traps attract flies to a container they are unable to escape. Don’t place odor traps inside or near barns, as they attract flies; instead place them around the perimeter of pens.

Premise sprays are insecticides with residual activity that are sprayed on surfaces. The flies are killed when they land on these treated surfaces. Fly baits contain attractants mixed with insecticide that can be set up in bait stations, as a scatter bait, or mixed with water and applied to surfaces.


The importance of environmental management in order to minimize fly breeding areas cannot be overstated, especially for confinement operations. In the pasture setting, encourage water drainage and minimize decaying plant matter with cutting or burning. In confinement areas, manure, damp and soiled hay, uneaten grain and any other source of decaying organic matter should be removed weekly at a minimum and scattered to dry. Proper cleaning and addressing damp areas will reduce fly breeding sites, disrupting the fly life cycle, and will have a significant impact on fly numbers.

Complete environmental cleaning and modification to eliminate fly breeding sites is ideal to strive for; however, this is almost never practical. Fly predators are small insects that can provide excellent environmental control (as a supplement to cleaning) by naturally killing immature flies, reducing fly numbers. Fly predators should be scattered in areas that flies will lay eggs: manure piles, under bunk lines, along creek banks and anywhere there is decaying or moist organic matter. For optimal control, you can add more fly predators monthly.

It can be difficult to tell if your control efforts are having a positive impact, but I can assure you they are. We have data on the increase in production (and profits) as a result of good fly control, so the investment of time and in the products to control flies is well worth it. Be sure to use a variety of control options and always follow label instructions, and you will be well on your way to controlling those pesky flies.   end mark

PHOTO: The importance of environmental management in order to minimize fly breeding areas cannot be overstated, especially for confinement operations. Courtesy photo.

Tony Hawkins
  • Tony Hawkins

  • Technical Service Veterinarian
  • Valley Vet Supply