Biting flies are a problem in region

The nice weather has been enjoyable, but with decent temperatures comes the buzzing and biting of flies. Besides being annoying, flies are known to be a source of disease dispersal and discomfort which can affect cattle production. "It's an anima...

The nice weather has been enjoyable, but with decent temperatures comes the buzzing and biting of flies.

Besides being annoying, flies are known to be a source of disease dispersal and discomfort which can affect cattle production.

"It's an animal care and production issue," Dickinson State University Agriculture and Technical Studies Department Chair Dr. Chip Poland said. "Flies are an irritant and if the animal is spending more time dealing with the irritation than grazing and growing, that affects production."

The window of opportunity for flies to buzz around North Dakota compared to other states is less, but it doesn't stop the insects from making their homes where they can.

Poland said the most irritating for animals are face flies and heel or biting flies.


"Face flies can transmit diseases such as pink eye from one animal to the other," Poland said. "Flies are carriers and tend to affect certain breeds of cattle. Those with dark colored faces have fewer problems than whiter faces, but some producers may disagree. Stereotypically, those with whiter faces have more problems with pink eye."

Horn and stable flies were the recent focus of an article by North Dakota State University Animal and Range Science Extension beef cattle specialist Dr. Greg Lardy, NDSU entomologist Janet Knodel and Ellen Crawford with NDSU Agriculture Communication.

Horn flies lay their eggs in and under manure pats to be ready with adult flies for the following spring.

The Lardy, Knodel and Crawford article states the horn fly population usually peaks in late July and August. The bugs are particularly severe in southcentral and southwestern North Dakota, but are known to affect all regions of the state.

Horn flies are grayish and half the size of houseflies. They cluster on cattle horns, shoulders and backs, moving to the animal's belly during hot or rainy weather.

Horn flies stick like glue to cattle, feeding 20 to 30 times a day. The blood-thirsty creatures are not only a pain, but can create anemia from blood loss, resulting in weight loss and a weakened animal.

Lardy is not sure exactly why the southern portions of the state are seeing more severe problems with the flies this year.

"It probably had something to do with the moisture we received early in the growing season and the (favorable) environment it created for fly reproduction and larvae survival," Lardy said.


Dickinson Research Extension Center Livestock Research Specialist Garry Ottmar agrees the flies are worse this year at the center's ranch in Manning.

"They weren't here as early as they have been in other years, but when they came they were really bad," Ottmar said. "The worst time for them is in July and August."

Insecticide ear tags are one control method and contain a synthetic pyrethroid or organophosphate. At the DREC ranch, Ottmar said they put the ear tags on during the second or third week in June.

"You don't want to put ear tags in too soon, otherwise the insecticide runs out in August and you still need control in September," Ottmar said. "You can purchase the tags at any animal health store."

Each ear gets one tag, he added.

"You put one on the back of the ear so when they fight the flies with their heads, the tags touch the animal's back to spread the insecticide," Ottmar said. "Tags work really well. We've been using them for years."

A less hands-on, but more labor intensive option is what Ottmar calls, "cattle oilers" where the livestock walk underneath the oiler and rub on them to spread insecticide on the animal.

Poland and Ottmar agree older methods such as backscratchers aren't used much anymore.


Another choice for producers is feed additives which inhibit flies' from reproducing in and under manure pats.

"That product is fed to the cattle and tend to lead to less fly production," Poland said. "You need to find what works best for your operation. What works for one doesn't always work for another and control is tailor made to an operation."

Feed additives pass through the digestive system, destroy the developing fly maggots in manure and can kill up to 80-90 percent of larvae, preventing maggots from maturing into adults. The only exception to this method is fly migration from herds not treated by the additives.

"Data suggests if a control technique for flies is implemented strategically it is cost effective," Poland added.

Dickinson's Dean Karsky has a commercial dairy operation, but doesn't use additives or ear tags for his cattle.

"A guy comes in and sprays inside and outside of all the buildings, which works best since most of our cows are inside," Karsky said. "He comes once a month to spray starting in May until September."

The Karskys haven't needed to do anything else for their operation, he added.

Choose at least 15 cattle to count the number of flies on heads, backs and shoulders to see how bad flies are with a herd. Using binoculars, if more than 100 flies per animal can be seen, then control is needed.


Insecticide resistance is one thing producers want to avoid when controlling fly irritation. To do so, producers should remove tags before frost is present, not use tags until horn flies are present and rotate insecticide classes in tags annually.

Ottmar said tags are removed between September and October and he fits new ones in the spring. The new ones go in the same holes so another hole isn't made in the animal's ears.

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