Cattle and Flies

If you are not seeing flies on your cows right now, you soon will be! Each Spring brings in rain, new grass growth and a new wave of flies. There are three main fly species that will impact your cattle; the horn fly, the face fly, and the stable fly. Flies can cause economic losses in many ways but their feeding and presence on the animal both negatively impact the weight and comfort of the animal making them less productive. As cattle try to rid themselves of the flies by moving, swatting with their tail, or slinging their head back, they are burning energy and stressed by having to deal with them. These disturbances can result in 5 to 25 pounds of weight loss on both calves and adults. It is important to know what flies you deal with, the time it takes for them to complete a life cycle and at what level these flies will begin to negatively impact your cattle and warrant a control measure. While it is hard to count each individual fly (I would really like to meet the person that could), the fly count does not have to be precise but is used as a recommendation.

Horn flies are small and are typically seen on the backs, sides, and belly of the animal. Horn flies feed on the animal’s blood taking up to 30 blood meals in a day. Their typical life cycle is between 10-20 days. The time to control horn flies is if the fly count exceeds 200 flies per animal, but you will likely want to start controlling at around 150 or so before it gets to that point.

Face flies are a little larger than a house fly and you guessed it, congregate on the animal’s face. These flies will feed on the fluids that the animal secrets from its eyes, mouth, nose, and any wounds. They are also known to aid in the spread of pinkeye. The life cycle for face flies is around 12 to 24 days. It is hard to know when to effectively treat face flies as they may spend very little time on the animal only coming to feed then leave but being mindful and watching for them in the cool parts of the day will help you decide when and if to treat.

Stable flies tend to congregate around the front legs of the animal but can also be found on their belly. Their bites are very painful and may cause the animals to gather in bunches or stand in water to avoid being bitten. Because of this, the fly count before treating may be as low as 5 flies per leg. The stable fly’s life cycle will be around 14 to 24 days.

While they are all three hard to deal with, they can be controlled. Back rubbers, insecticidal ear tags, special minerals for the cattle, and pump sprayers can all be used to help control fly populations. Back rubbers and pump sprayers require that you purchase the chemical to be applied to the animal. Many producers use products that contain Permethrin which does a good job at controlling fly populations. If using insecticidal ear tags, it is recommended that each ear receive a tag to provide up to 5 months of fly control. You can use just one tag but must understand that it will not provide optimum control. To ensure that the flies do not build an immunity, make sure to change the product you use every year for a rotation. Using cattle minerals with an IGR to control flies is a bit tricky. The way they work is by keeping the larvae in the fecal droppings from growing into mature adults. Fool proof, right? Well, if this is your only means of controlling flies and your neighbor does not control theirs, adults can fly over to your property and pester your cattle. Using a mineral with IGR works best when your property is more or less secluded from others and/ or you also use a previously mentioned control measure in conjunction with it.

For more information on cattle management, contact the Texas A&M AgriLife Extension Service at (936) 560-7711, or visit our website at

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