Summer months tend to bring hot weather and conditions that kill off many types of fly populations. But that doesn’t mean you won’t still see your cattle swatting at flies all summer through. How do you control flies all year round at the farm? Eldon Cole, University of Missouri Livestock Specialist, and Johnny Gunsaulis, University of Arkansas County Extension Agent, both weighed in on this topic.
In the Ozarks, there are four prominent types of fly populations that affect livestock. “The specific types we run into most are the stable fly, horn fly – by far the most numerous of our flies; the face fly – which is usually viewed as a real bad guy when it comes to transmitting pink eye from one animal to another; and the horse fly. Some flies are harder to control than others, and the control for one might not work for another,” explained Cole.
The easiest type of control is for the horn fly. Gunsaulis cited a University of Arkansas trial that found that when an animal has 100 horn flies on them it can reduce the calf weaning weight by 17 pounds. “It can be worth running them through the chute and putting a fly control tag at $3 a piece – that seems like an easy pay off,” he said.
Six fly control options for different species:
1. The pesticide treated fly tag – a tag for one ear or both

Cole explained these tags are “good for a little while, and there are different lengths of goodness for different tags.” He noted that producers tend to want to put them in really early in the spring, and by the time the real fly numbers start coming a lot of the goodness of that tag has disappeared. “We’ve encouraged folks to put the tags in later in the spring and early summer, if they have the opportunity.” Gunsaulis warned against pesticide resistance buildup through these tags. He recommends going between an organophosphate tag and a cyflutherin from year to year.
2. A “feed through” pesticide – an item put in mineral or in feed that is used to interrupt the development of flies in the animal’s manure.
This product is not going to take care of the flies on the animal; instead it interrupts the fly’s development and cuts down on the total number of flies on the farm. “This approach is fairly expensive, and some cattle don’t eat as much mineral as others, so intake is a bit of a problem. It’s also a little more expensive. However, long term it can be a good help,” Cole noted.
3. Self-applicating devices such as a back rub or dust bags.
“A lot of farmers will say, ‘my cattle won’t use them, I don’t have any place I can put them where they rub through them on a regular basis,'” Cole noted. You want cattle to use them every couple of days or so. Placing them around a water hole or mineral feeder, or where the animals are going through from one pasture to another can be good options for placement.” Cole said it is an effective method that is underutilized. Also, he noted, for face flies specifically, you’d have to have some apparatus that will allow the pesticide to get on the animal’s face if you’re going to combat face flies and prevent pink eye spread.
4. Sprays
“Modern technology has brought on misters or fine sprayers that you can mount on the back of a truck and you can mist them with the pesticide every now and then,” Cole said. However, he noted, you have to consider the weather as rain will limit length of time it is active.
5. Biological controls (no pesticides) great for barns
“Around barns the house flies are terrible this year,” Gunsaulis noted. “One thing we’ve done at one of our facilities is bring in parasitic wasps that you can order by mail. This is a small parasitic wasp that lays its egg in the fly’s egg casing and the wasp develops faster than the fly and kills the developing fly. Barns where they keep animals year round can benefit from this type of control.” And, Gunsaulis noted, this is a tiny wasp that doesn’t move very far; it will never be a nuisance to the people around. “We used Beneficial Insectary out of California; they shipped the wasps based on how many animals are in your facility. We got weekly shipments and then sprinkled around the eggs, and when they hatch they parasitize the other casings.”
6. Horn fly trap
Both Gunsaulis and Cole noted an old mechanism that is becoming popular again, the horn fly trap. “There is an old design of a fly trap I’ve seen and we’ve looked at at some dairies that can provide some control. The flies actually get caught in a trap, and while it does not offer 100 percent control, if cattle have to go through the chute where the trap is a couple times a day, it can help reduce the population without pesticides,” Gunsaulis said. Cole noted a horn fly trap looks like a cattle working chute with special louver inside that ensures the flies are scared off the back of the animal as it goes through the chute, then they get caught in the trap. The University of Missouri Extension has a publication that gives step-by-step instructions on how to build a horn fly trap. It is entitled, “Walk-Through Trap to Control Horn Flies on Cattle” and can be accessed at Ozarks Farm & Neighbor’s website.
Gunsaulis concluded by saying that the economics of fly control bear out. “It used to be the economics of fly control on a dairy operation and beef operation were different, but they’re getting closer to same with horn flies in particular. If 100 horn flies decrease weaning weights by 17 pounds, and you put the value of that calf at $1 or $1.50 a pound, then that is a pretty good return to prevent that loss. And, when you run the animals through the chute, there are a lot of other things you can do at same time, blackleg, lepto, depending on your animals.” Fly control doesn’t have to be an added burden, and not attending to these pests at your farm can have major economic consequences.


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