It’s summer, and the fly wars are on

Controlling flies now pays dividends later.

July 18, 2018

2 Min Read
It’s summer, and the fly wars are on

By Grant Dewell

Summer is supposed to be the time when your cattle enjoy good weather, good pastures and easy living. But to be frank, summer also brings hot weather, flies, pinkeye and anaplasmosis…and then more flies. The fly wars are on and here are some tips to help you and your cattle cope.

Fly population have been steadily building and from now until fall we will see peak fly problems. Instituting some sort of fly control program (sprays, oilers/rubbers or fly tags) will help decrease flies that spend a lot of time on cows such as horn flies and some face flies. Stable flies and other biting flies do not spend much time on cows so you need to focus on environmental controls not just topical treatments.

Good fly control can help cows by not only limiting impact from bites on production, but because cows will group up to avoid flies, it can increase the negative effect of heat stress as cows have to choose between staying cool or not getting bit as much.

This is the time of year when pinkeye problems in calves are hitting their peak. This happens for several reasons: Face flies are numerous, colostral immunity has reached its end and the calf’s own immune system is still developing, and there is some tall grass with pollen that can irritate eyes.

Related:Can we select cattle for fly resistance? Research says yes!

To beef up the calf’s immune system, a booster dose of pinkeye vaccine would be good to give now plus focus on fly control in calves. Many of the fly control methods for cows (fly tags, oilers, etc.) may not reach the calf. Having some face wipes at the entrance to creep feeders may improve fly control on calves.

The increased biting fly population is also starting to spread anaplasmosis organisms around if it is in or near your herd. Susceptible cows may develop clinical signs such as anemia, jaundice and sometimes sudden death.

Although horn flies can transmit some anaplasmosis, the biggest concern is stable flies and ticks, so normal fly control has limited value. If you are in an endemic area, you may want to consider having your veterinarian write a VFD for chlortetracycline (CTC) to protect your cow herd.

Grant Dewell Is Iowa State University beef Extension veterinarian.

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