Methods to combat horn flies in cattle herds
The horn fly is an important pest due to the negative impact it can have on cattle and producers’ bottom lines. According to researchers at the University of Arkansas, horn flies cost cattle producers $2.3 billion annually in losses. Horn flies impact weaning weights, stocker gains, and contribute to mastitis.
There are a variety of methods producers can use to combat horn flies. Depending on the operation and producer, some methods will work better than others.
Insecticide Impregnated Ear Tags
There are currently three classes used in insecticide impregnated ear tags: organophosphates, pyrethroids and macrocyclic lactones. It is important to rotate all three of the classes of insecticide ear tags from one year to the next to prevent resistance. Choose one insecticide class to use for the first year then move to another class the following year, the third class the next year, and then start back with the class utilized the first year.
Self-Treatment Devices (back rubbers or dust bags)
The most effective way for producers to use back rubbers or dust bags is through forced use. The treated back rubbers or dust bags should be placed in a gateway where animals must go through daily to get to water or mineral.
It is better to use dust bags in pairs, so animals will get treated on both sides. Generally, the bottom of the dust bag should be 4 to 6 inches below an animal’s topline.
Feed-through Larvicides and IGRs
IGR (insect growth regulator) feed throughs are ingested by the animal after it is mixed with mineral or top-dressed on feed ration. The IGR passes through the animal into manure, then when larvae hatch, the IGR inhibits growth and larvae never make it to adulthood.
A new IGR product is now available. A reformulation of the IGR bolus is approved and on the market. The IGR bolus, Altosid IGR XRB, lasts a little over 180 days. The IGR bolus may be a viable option for producers looking for more consistent results with IGR products; mixing IGRs with mineral can have its downsides.
“The IGR products can work very well. But with mineral, sometimes cattle will decrease consumption in the summer or quit eating their mineral so once that happens the IGR is not as effective. With the bolus you don’t have to worry about that because it is a sustained release bolus that stays in the stomach,” Kelly Loftin, Ph.D., University of Arkansas profes-sor and entomologist, said.
Additionally, all IGRs generally work better if the herd is isolated from untreated herds. “If there are untreated herds across the fence, chances are the producer is not going to be happy with the level of control because it has no impact on adult flies that are feeding,” Loft-in said.
Pour-ons
Pour-ons contain a higher insecticide concentration than sprays. The two most common types of pour-ons are pyrethroids and endectocides. “I don’t recommend producers rely on endectocides alone to control horn flies because the endectocides also target internal par-asites. So, if you are applying a pour-on to keep your horn flies under control you are making more frequent applications which can help facilitate resistance in the internal parasites,” Loftin explained.
Sprays
There are two traditional forms of spray fly control. First, there are the high-pressure sprays in which the producer is applying a large volume of insecticide, approximately a quart and a half per animal. Next, there are low-volume sprays that apply 2 ounces per animal. The low-volume sprayers are typically exit or solar powered walk-through sprayer systems.
Trapping
Another method of fly control is trapping. This method is typically used in organic opera-tions. In this method, there is a passive trap and as animals pass through it, it dislodges the flies. The flies are attracted to the light in the sides of the trap and the flies get caught and cannot get back to the animal.
Counting
An important thing producers can do is to learn how to estimate the number of flies they have per animal. According to Loftin, the treatment threshold is about 200 horn flies per an-imal. If producers roughly count and monitor the fly population on their animals, then they will be able to notice changes in that population and determine if their treatment products are working.
