Cattle are not a fan of flies. I know this seems like an obvious statement, but it is one that is often understated. Just because it is normal for flies to hang around on cows doesn’t mean they should be ignored. Flies can cause so much irritation to calves that they grow more slowly. They also spread a nasty disease called pinkeye, which can make cattle blind. Because of this, ranchers and farmers take steps to lower the amount of flies that are on cattle by using multiple fly-fighting strategies.
Good fly control always starts with the environment. Flies like to breed in places like old hay bales or manure patties. While it is impossible to get rid of all the manure (especially if the cattle are on pasture), old hay bales are disposed of when they no longer have any feed value. If cattle are on pasture, one way to make the manure inhospitable to flies is to feed the cattle an Insect Growth Regulator (IGR) in their mineral suppliment. This causes the eggs the flies lay to become unable to mature, making the manure a bad place for maggots.
Another option for controlling flies in the environment is to use parasitic wasps. These wasps cannot sting people. They lay their eggs in the pupae of the flies, which kills the fly pupae. The wasps do a better job with confined cattle, since the flies are more concentrated than they are on pasture.
Even with managing the environment, often the cow herself needs to be treated to keep the flies off her. There are actually multiple species of flies that attack cows. Each species congregates in a certain area on the cow. Therefore, in order to control flies the cow has to be treated with more than one type of fly repellant.
Fly tags are the best way to keep flies off a cow’s face. They are placed in the ears and are worn like an earing. Fly tags last for a few months, so they are usually put in at the start of the summer (since summer is the worst time for flies) and removed in the fall.
To keep flies off of the cattle’s body, ranchers can use a back rubber. These look like a big cloth tube and are draped over a gate that cattle walk through every day, such as the gate to the watering tank. The back rubber is filled with fly repellant, so when the cattle walk under the back rubber the fly repellant is rubbed off on their backs.
Another option is to use a fly spray. The fly spray can be applied directly to the cow’s body (a lot like you would put mosquito repellant on) and typically lasts for a couple weeks. The difficult part is that it has to be re-applied on a regular basis.
There are several other fly control methods that farmers and ranchers use, but the key point is that they use more than type to get the job done. By keeping the fly levels low, it makes our cows more comfortable and makes it less likely they will get pinkeye.